Sustainable bioenergy options for Mexico: GHG mitigation and costs

Sustainable bioenergy options for Mexico: GHG mitigation and costs

Renewable and Sustainable Energy Reviews 43 (2015) 545–552 Contents lists available at ScienceDirect Renewable and Sustainable Energy Reviews journa...

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Renewable and Sustainable Energy Reviews 43 (2015) 545–552

Contents lists available at ScienceDirect

Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser

Sustainable bioenergy options for Mexico: GHG mitigation and costs Carlos A. García a,n, Enrique Riegelhaupt b, Adrián Ghilardi c, Margaret Skutsch c, Jorge Islas d, Fabio Manzini d, Omar Masera a a Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Antigua Carretera a Pátzcuaro No. 8701, Colonia Ex-Hacienda de San José de la Huerta, 58190 Morelia, Michoacán, Mexico b Red Mexicana de Bioenergía A.C. Av. San José del Cerrito, 400-51 Col. El Pueblito, CP 58341 Morelia, Michoacán, Mexico c Centro de Investigaciones en Geografía Ambiental (CIGA), Universidad Nacional Autónoma de México (UNAM), antiguacarretera a Pátzcuaro 8701, Morelia CP 58190, Michoacán, Mexico d Instituto de Energías Renovables, Universidad Nacional Autónoma de Mexico, Privada Xochicalco S/N, Colonia Centro, Temixco, Morelos 62580, Mexico

art ic l e i nf o

a b s t r a c t

Article history: Received 12 May 2014 Received in revised form 12 August 2014 Accepted 8 November 2014 Available online 28 November 2014

Appropriately implemented bioenergy could be a renewable source of energy contributing to fossil fuels substitution and greenhouse gas (GHG) mitigation in Mexico. This work explores eleven bioenergy options with environmentally sustainable biomass production potential. Mature and widely used technologies for biomass transformation are selected. Mitigation costs and investments are calculated for each option. The options cover electricity, heat, and mobile power for use in the agricultural, industrial, transport, services and residential sectors. By the year 2035 the set of bioenergy options considered could replace 16% of the final energy consumption currently provided by fossil fuels, and could mitigate 17% of GHG emissions compared to the baseline. Wood pellets for industrial, efficient cook stoves and efficient charcoal kilns show negative mitigation costs and low investment requirements, and are thus promising as regards implementation in the short to mid-term. Liquid biofuels on the other hand show high mitigation costs and low to high mitigation potential, depending on the feedstock, although most of these options also offer important sustainable development co-benefits. & 2014 Elsevier Ltd. All rights reserved.

Keywords: Energy systems Carbon emissions Sustainability Potential Land use

Contents 1. 2.

3.

4. 5.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. Sustainable biomass production potential in Mexico. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2. Selection of technologies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3. Fossil fuel substitution and greenhouse gas mitigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4. Mitigation costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. Potential of the bioenergy options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. Future share of bioenergy options in Mexico. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3. GHG mitigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4. Mitigation costs and investments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

546 546 546 547 547 547 548 548 549 549 549 550 551

Abbreviations: BAU, business as usual; CFE, Comisión Federal de Electricidad (public electric company); CH4, methane; CO2, carbon dioxide; CO2e, equivalent carbon dioxide; DM, dry matter; DOE-EIA, Department of Energy-Energy Information Administration; EUF, energy use factor; gCO2e, gram of equivalent carbon dioxide; GHG, greenhouse gas; km, kilometers; LCA, life cycle assessment; LULCC, land use land cover change; M, million; MAI, mean annual increment; Mbpd, million barrels per day; Mha, millon of hectares; MJ, megajoule; MtCO2e, million tonne of equivalent carbon dioxide; MUSD, Million of United States Dollar; MW, megawatt; NPV, net present value; PEMEX, Petróleos Mexicanos (public petroleum company); PJ, Petajoule; RE, renewable energy; t, tonne; tCO2e, tonne of equivalent carbon dioxide; TW h, terawatt hour; USD, United States Dollar; yr, year n Corresponding author. Present address: Escuela Nacional de Estudios Superiores Unidad Morelia, Antigua Carretera a Pátzcuaro 8701, Col. Ex-Hacienda de San José de la Huerta, Morelia CP 58190, Mexico. Tel.: þ52 443 3222709. E-mail addresses: [email protected], [email protected] (C.A. García). http://dx.doi.org/10.1016/j.rser.2014.11.062 1364-0321/& 2014 Elsevier Ltd. All rights reserved.

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Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551 Appendix A. Supporting information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 551

1. Introduction The Mexican energy system is based on fossil fuels, which supply 92% of the primary energy (65% from oil, 24% from natural gas and 2% from coal) [1]. Mexico holds the 14th place in absolute terms among GHG emitting countries [2]. National energy security is currently at risk, since crude production fell from 3.8 million barrels per day (Mbpd) in 2004 to 2.5 Mbpd in 2011 [3] and it is uncertain whether current exploration efforts will lead to the discovery of the levels of proven oil reserves and high production that have marked the past decades [4]. As for natural gas, domestic production is also insufficient, imports accounted for 33% of national consumption in 2011 [3]. Although Mexico ranks fourth in the list of countries with potential shale gas reserves [5], there is uncertainty about the real size of these reserves, as well as the economic viability of their exploitation and the associated environmental impacts. In response to this situation, the Mexican Government has focused efforts on increasing oil and gas prospecting and extraction [6,7] giving much less attention to renewable energy (RE) sources, whose potential contribution to mitigation of GHG and energy security has not yet been properly acknowledged. However, a goal of 35% share of RE plus nuclear power in the electricity mix for year 2024 has already been set [8]. Moreover, the Mexican Climate Change Law of 2012 set goals for reducing GHG emissions by 30% in 2020, and 50% in 2050, taking 2000 as baseline year [9]. In 2010, the share of biomass in Mexican primary energy supply was 4.3%, mainly relating to the use of fuelwood by households and bagasse by the sugar industry [1]. Fuelwood is used for cooking by about 25 million people, mostly in rural areas, but also in many small scale industries and shops such as charcoal making for commercial and residential grilling, brick and tile kilns, bakeries, mezcal, pottery, tortillas, among others [10]. Most of the biomass technologies presently used in Mexico have low efficiencies and are harmful to human health as a result of smoke pollution and in some cases to the environment, as a result of deforestation. However, experience from other countries demonstrates that efficient and clean technologies can be introduced [11–13]. In the area of renewable energy in Mexico, most public attention has focused on liquid biofuels for transportation, but there are many other mature technologies, such as processed solid biofuels (fuel-chips, wood pellets, charcoal) which could be used to produce electricity, industrial and household heat, pig iron, ceramic materials, among others. In view of the negative environmental impacts of fossil energy sources, RE options should aim to achieve positive impacts on climate change. In the case of bioenergy, sustainability needs to be considered as a critical aspect, because depending on the specific option, bioenergy development can pose risks such as biodiversity loss [14– 16], deforestation and increased CO2 emissions due to land use change [17–19] soil erosion, depletion and contamination of aquifers [20,21], high costs [22], and deterioration of food security [23]. Developing “what-if” scenarios is a useful way to explore energy options and their potential impacts. Several published articles have applied this tool to bioenergy [24–27], in Mexico [10,26] as well as in other countries (e.g. [28]). However, most of these studies have not considered sustainability criteria when assessing biomass production potential, and did not perform cost analysis.

In this work, we built two scenarios to explore the long-term impacts of bioenergy in Mexico. The first is the business as usual (BAU) projecting current trends up to the year 2035 in the sectors in which bioenergy options are proposed. The second is the Alternative scenario that is composed of eleven options for bioenergy replacing fossil fuel use or increasing the efficiency of fuelwood end-use devices in the residential sector. The alternative scenario was constrained by a set of environmental and socioeconomic sustainability criteria regarding both the biomass production potential and the technologies for transformation and end-use. We calculated primary energy demand and GHG emissions between 2015 and 2035 for both scenarios. To explore the financial viability of bioenergy options, we performed detailed benefit/cost analyses.

2. Methodology 2.1. Sustainable biomass production potential in Mexico Three bioenergy sources were considered: (1) sustainable forests management of natural forests as a source of woodenergy (direct wood-energy), (2) wood-energy as a byproduct of current forest operations (indirect wood-energy), and (3) energy plantations. The sustainable production of wood-energy from native forests was calculated as the potential woody biomass annual growth (or Mean Annual Increment, MAI) usable for energy purposes. The organic carbon in forest biomass stock and soil are assumed to remain constant in time. MAI assumptions depend on forest type and annual rainfall. Only a fraction of MAI is assumed to be usable for energy, indicated by an energy use factor (EUF) by forest type. The EUF depends the extent to which higher value-added wood products (e.g. for construction, furniture and paper) compete for the use of the timber. Only forests near settlements (less than 5 km radius), near major and interconnected roads (less than 3 km each side), and over flat areas (less than 30% slope) were considered suitable for management for bioenergy. Protected and high conservation value areas [29] were excluded. Indirect wood-energy a by-product of commercial forest logging and sawmilling, was calculated as 0.3 of the dry weight of logged wood plus 0.5 of logs processed at sawmills. Energy plantation potential was calculated on the basis of the area available for expansion of five crops: sugarcane, grain sorghum, Jatropha curcas, oil palm, and Eucalyptus spp. Three yield levels were defined for each crop, depending on hydric balance and soil quality (see Supplementary material for details). Each crop was assigned only to areas where it shows high yields, calculated on the basis of climatic conditions (maximum and minimum temperatures, frost period, number of dry months), soil quality and terrain slope. Three exclusion criteria (masks) were applied to determine areas not suitable for each crop, other than those previously mentioned above: (1) altitude; (2) slopes; (3) frost frequency. In addition 3 sustainability criteria were set: (1) areas not requiring irrigation, (i.e. only rainfed areas are considered suitable; (2) protected areas are not suitable; and (3) only grasslands and pasturelands were considered suitable for dedicated energy crop establishment, assuming a nationwide transition from extensive to

C.A. García et al. / Renewable and Sustainable Energy Reviews 43 (2015) 545–552

intensive livestock farming within the analysis period. Moreover, all areas presently planted with food crops were excluded. Supplementary material gives a more detailed explanation of the methodology and data sources employed. 2.2. Selection of technologies We selected only proven and commercially available transformation and end-use technologies, for which consistent information is available about conversion rates, yields, and costs. Additionally, we covered a wide span of energy demands: electricity, heat and mechanical power, in diverse economic sectors: agriculture, industry, transport, services and residential. This assessment was not intended to cover the full technological spectrum, but rather to explore whether sustainable bioenergy is worth developing in Mexico in terms of its energy potential and costs. Table 1 summarizes the technologies selected for each source of biomass and end-use. Table 2 shows technology application in different sectors. 2.3. Fossil fuel substitution and greenhouse gas mitigation To explore the long-term impacts of bioenergy in Mexico we built eleven trend lines reflecting current fossil fuel or traditional biomass use in specific sectors of the economy: electric generation (limited to fuel oil and coal), fuel oil use in industry, coke used by pig iron plants, gasoline and diesel for transport sector, traditional fuelwood use and charcoal production. These trend lines were built using official data and projections of population growth, assuming Gross National Product growth at 3.5% per year, and present levels of energy consumption and emissions of each sector or activity (see Supplementary material). For each trend line we proposed a bioenergy technology option (see Table 2) that replaces the use of fossil fuels, or that allows

547

more efficient biomass use. For each of the technologies we used simple penetration rates, either linear or logistic. Fossil energy saving is the difference between the primary energy consumption in the bioenergy option and in the trend line, while greenhouse gas mitigation is the difference in emissions. Only tailpipe or smokestack emissions were accounted for, so the values reported correspond to gross mitigation potential (see Supplementary material for emission factors). This means that emissions from land use change, crop cultivation and harvest, feedstock collection and transport, industrial processing and transport to gasoline mixing facilities (in the liquid biofuel cases) are not accounted for. The BAU scenario is the sum of the eleven trend lines, while the Alternative scenario is the sum of bioenergy options. Total fossil fuel substitution and mitigation potential was calculated as the difference between the BAU and the Alternative scenario. For all the technical and environmental data we refer the reader to the Supplementary material. The base year for the scenarios is 2010 due to the availability of information; however we assume that bioenergy technologies begin to operate from 2015.

2.4. Mitigation costs To assess the mitigation costs we used the Net Present Value (NPV) of the cash flow of each option, built by deducting expenses (investment, operation and maintenance costs, inputs and services consumed) from incomes (obtained from the sale of energy carriers and by products, plus salvage value of investments in year 2035) in a time series 2015–2035. Incomes and expenses are in US Dollars of year 2007, and NPV was calculated using a 10% discount rate. The projected prices of fossil fuels in the Mexican market were obtained from Mexican official sources. Sea-freight costs

Table 1 Bioenergy selected options. Transformation technology or process

Description

Co-combustion of biomass

Imported coal replaced by fuel wood harvested by sustainable management of existing forests in a radius of 300 km around a coal power plant Direct combustion New power plants to be fueled by coal and natural gas are replaced by wood-fired facilities, using fuel from sustainably managed native forests Direct combustion Eucalyptus plantations established as new carbon sinks and fuel producing areas in (Plantations) deforested lands, to feed wood-fired power plants Efficient charcoal kilns (for In this intervention coke used by pig iron plants is partially replaced by charcoal in pig-iron industry) two ways: a) sintering of iron ore fines with charcoal fines, and b) fueling the blast furnaces with a mix of coke and charcoal Wood pellets burned for Sawmill waste used to produce wood pellets, which will replace diesel and fuel oil in heat industrial boilers and ovens Efficient cook stoves This intervention assumes substitution of traditional cook stoves used by rural families by more efficient stoves. These are improved devices with enhanced cooking and space heating performance. Efficient cook stoves reduce fuelwood consumption and in some areas the non-renewable fraction of fuelwood harvested Efficient charcoal kilns This option is based on the replacement of traditional earth-mound kilns by brick kilns, which are more efficient in converting wood to charcoal, and the introduction of sustainable forest management in the forests where charcoal is produced Fermentation (ethanol Ethanol from sugarcane juice to partially substitute gasoline from sugarcane) Fermentation (ethanol Ethanol from grain sorghum to partially substitute gasoline from grain sorghum) The oilseeds of Jatropha curcas as a source of biodiesel replacing fossil diesel Transesterification (biodiesel from Jatropha curcas curcas) Transesterification Oil extracted from palm fruits converted to biodiesel to replace diesel (biodiesel from palm oil)

Main assumptions

2775 MW coal power plant, 10% (in energy) co-firing with fuel wood at 2035 Linear penetration, 7612 MW wood fuelled plants. Managed forests 26.3 Mha at 2035 Linear penetration, 1571 MW fuelled by plantation wood grown on 0.51 Mha by 2035 Linear penetration, 20% share of charcoal in sintering and fuelling by 2035 Linear penetration, wood pellets substitute fuel oil and diesel use in industry Linear penetration of efficient cook stoves to achieve 90% substitution by 2035

Linear penetration and 70% of charcoal is produced in efficient kilns by 2035 Logistic penetration, 2.9 Mha of new sugarcane planted to supply 139 ethanol plants in 2035 Logistic penetration, expansion of sorghum cultivation on 2.6 Mha to supply 28 ethanol distilleries by 2035 Logistic penetration, plantations expand to 3.2 Mha by 2035 to supply feedstock to 29 biodiesel plants Logistic penetration, plantations expand to 1.85 Mha in 2035 to supply feedstock to 117 biodiesel plants

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Table 2 Selected bioenergy options, end-use sector, energy categories and biomass source [PJ]. Transformation technology or process

Trend line end- End-use sector use energy carrier

Final energy consumption “replaceable” by bioenergy options

Bioenergy replaces fossilfuels?

Major energy categories

Biomass source

Bioenergy end-use energy carrier

Co-combustion of biomass

Coal

Residential, commercial, industrial

66

Yes

Electricity

Electricity

Direct combustion

Natural Gas, coal

Residential, commercial, industrial

273

Yes

Direct combustion (Plantations) Efficient charcoal kilns

Natural Gas, coal Coal

Residential, commercial, industrial Industrial: pig iron

(a)

Yes

117

Yes

Wood pellets burned for heat Efficient cook stoves

Fuel oil and diesel Traditional fuelwood

Industrial

125

Yes

Native forests under sustainable management Native forests under sustainable management Forest plantations: Eucalyptus spp. Native forests under sustainable management Sawmill residues

Residential: for everyday cooking and heating

241

No

Fuelwood

Efficient charcoal kilns

Traditional charcoal

26

No

Fermentation (ethanol from sugarcane) Fermentation (ethanol from grain sorghum) Transesterification (biodiesel from Jatropha curcas) Transesterification (biodiesel from palm oil)

Gasoline

Residential: fuel off the grill, and commercial: restaurants Transport

3791

Yes

Native forests under sustainable management Native forests under sustainable management Sugarcane

Gasoline

Transport

(b)

Yes

Grain Sorgum

Ethanol

Diesel

Transport

1614

Yes

Jatropha curcas

Biodiesel

Diesel

Transport

(c)

Yes

Palm oil

Biodiesel

Total

Solid biofuels

Liquid biofuels

Electricity

Electricity Charcoal

Heat

Charcoal

Ethanol

6253

(a) Same as native forest electricity; (b) same as Sugarcane ethanol; (c) same as Jatropha curcas Biodiesel.

Table 3 Technical production potential of selected biomass resources in Mexico. Bioenergy option

Trend line end-use energy carrier

Co-combustion of biomass Direct combustion Direct combustión (Plantations) Efficient charcoal kilns (for pig-iron industry) Wood pellets burned for heat Efficient cookstoves Efficient charcoalkilns Fermentation (ethanol from sugarcane) Fermentation (ethanol from grain sorghum) Transesterification (biodiesel from Jatropha curcas) Transesterification (biodiesel from palm oil)

Coal Natural Gas, coal Natural Gas, coal Coal Fuel oil and diesel Traditional fuelwood Traditional charcoal Gasoline Gasoline Diesel Diesel Total

Potential (PJ)

a

Potential (PJ)

18 710 140 34 64 108 61 338 84 36 120

7 189 42 11 64 108 19 338 84 36 120

1713

1018

b

Area (Mha)

0.52

2.9 2.6 3.2 1.8 11.0

Note: Bioenergy potential of solid and liquid biofuels correspond to the energy content of the end-use energy carrier, such as fuelwood or ethanol for example. For the case of electricity and charcoal, only transformation loses are accounted (not distribution ones). a b

Neither transformation nor transportation loses are accounted for in electricity and charcoal. Transformation loses are accounted for in electricity and charcoal.

were taken from DOE-EIA [30], and Mexican road transport costs from the public electric company CFE [31–33]. Mitigation costs are calculated using Eq. (1):

3. Results

Mitigation Cost Optioni

Mexico has high technical potential for sustainable biomass production, totaling 1713 PJ or 18.5% of all primary energy used in the country in 2010 (1) (Table 3). Most of this corresponds to direct wood fuels from sustainable forest management (54.3%), followed by energy crops (41.9%) and sawmill residues (3.7%).

¼ NPV ð2007 USDÞ=Accumulated Mitigation Optioni ðMtCO2 eÞ ð1Þ

3.1. Potential of the bioenergy options

C.A. García et al. / Renewable and Sustainable Energy Reviews 43 (2015) 545–552

Table 4 Mitigation potential of bioenergy options (in MtCO2e).

1000

PJ

800

600

400

200

0 2015

549

2020

2025

2030

2035

Fig. 1. Share of bioenergy options in final energy use in Mexico, 2015–2035.

Option

Cumulative mitigation

Co-combustion of biomass Electricity from managed forests Electricity from plantation wood Charcoal for pig-iron Wood pellets for heat Efficient cook stoves Efficient charcoal kilns Sugarcane ethanol Grain sorghum ethanol Biodiesel from Jatropha curcas Biodiesel from oil palm

42 278 32 4 84 23 19 354 84 35 100 1055

Total

80

Charcoal may substitute only 10.9 PJ (9.3%) of the coke used for primary energy in iron and steel manufacturing by 2035. Efficient charcoal kilns may save 47.5 PJ of primary energy in charcoal making for residential use, because of higher wood-to-charcoal conversion. One option with marked effects on the demand for oil-derived industrial fuels is the production of wood pellets, which may replace all the fuel oil and 30% of the diesel fuel to be used by the industrial sector in the year 2035.

70

MtCO2e

60 50 40 30 20

3.3. GHG mitigation 10

20

15

20 1 20 6 1 20 7 1 20 8 1 20 9 2 20 0 2 20 1 2 20 2 2 20 3 2 20 4 2 20 5 2 20 6 2 20 7 2 20 8 2 20 9 3 20 0 3 20 1 3 20 2 3 20 3 3 20 4 35

0

Fig. 2. Cumulative mitigation for all the options in the alternative scenario, 2015–2035.

3.2. Future share of bioenergy options in Mexico Full implementation of the 11 options could result in the substitution of 1544 PJ of fossil fuels by 2035, excluding the biomass used in fuelwood and charcoal production (Table 2). The largest substitution potential corresponds to electricity from fuelwood. In the BAU scenario, final energy consumption “replaceable” by all bioenergy options increases from 3040 PJ in 2015 to 6253 PJ in 2035, implying that bioenergy (1018 PJ/yr) substitutes for 16% of fossil energy used in 2035, once all options are fully developed (Fig. 1), equivalent to the 20% of total final energy consumption in 2010 (4940 PJ). Wood-based electricity, both from sustainable forest management and eucalyptus plantations, would achieve 8879 MW of installed capacity by 2035, replacing 82% of the new capacity that CFE has planned to install in 2011–2035, to be fuelled with natural gas and super-critic coal. This option would avoid substantial emissions and imports of coal and natural gas. Eucalyptus plantations would provide fuel for 11.7 TW h in 2035, or 15.4% of power generated in that year. Co-combustion of wood in coal fired power plants may substitute 10% of these plants’ primary energy use, namely 18 PJ in 2035 or 1 M dry matter (DM) t/yr. Sugarcane ethanol may replace up to 8.9% of the gasoline to be used by year 2035. Sorghum ethanol may achieve only 2.2%. As regards biodiesel, oil palm may replace 7.4% of projected diesel consumption by 2035, but J. curcas only 2.2%. Fuelwood for the residential sector is the only bioenergy source that decreases its share in primary energy use (compared with its baseline), because of the increasing efficiency of the improved cook stoves.

In the BAU scenario, GHG emissions grow from nearly 200 MtCO2e in 2010 to 470 MtCO2e in 2035, mainly because of the increased use of gasoline and diesel oil, which account for 80% of all emissions. In the Alternative scenario, the introduction of bioenergy reduces the emissions by 80.1 MtCO2e, or 17% of the baseline level at year 2035 (Fig. 2). The relative importance of each option as a mitigation tool is quite variable. Liquid biofuels show mixed potential: – sugarcane ethanol may mitigate 8.7%, of gasoline emissions (plus 0.15%, if highly efficient power co-generation is implemented) and is the option with the highest mitigation potential; sorghum ethanol might add just another 2.2% mitigation in this sector by 2035; – palm oil biodiesel may mitigate 7.4% and J. curcas biodiesel only 2.2% of diesel emissions by 2035. On the other side, some options have high mitigation potential in their respective sectors and end-use: – wood-based electricity may mitigate 62% of projected emissions for 2035; – wood pellets for industrial may mitigate 50% of the baseline emissions by 2035. Other options show intermediate mitigation potential compared with the trend line, such as electricity from eucalyptus plantations (10%), wood co-firing (10%). Cumulative mitigation reaches 1055 MtCO2e. The options sugarcane ethanol and electricity from managed forests have the largest mitigation potential (Table 4). 3.4. Mitigation costs and investments Five of the options show negative mitigation costs, i.e. have positive net benefits; four of them involve woody biomass used for electricity and heat generation. Two options show mitigation costs

10.0

5.0

Charcoal for pig-iron industry

Biodiesel from Jatropha curcas

Grain Sorghum ethanol

Sugarcane ethanol Co-combustion

15.0

Pellets

USD/tCO2e

20.0

Efficient charcoal kilns

25.0

Electricity from managed forests

30.0

Electricity from forest plantations

35.0

Biodiesel from palm oil

C.A. García et al. / Renewable and Sustainable Energy Reviews 43 (2015) 545–552

Efficient fuelwood coockstoves

550

0.0

- 5.0

-10.0 0

200

400

600

800

1000

Cumultive mitigation MtCO2e Fig. 3. Cumulative mitigation and unit costs of bioenergy options.

Table 5 Investment cost of bioenergy options (MUSD).

Option

Charcoal for pigiron Co-combustion Efficient charcoal kilns Wood pellets for heat Efficient cook stoves* Biodiesel from Jatropha curcas Biodiesel from oil palm Grain sorghum ethanol Electricity from plantation wood Sugarcane ethanol Electricity from managed forests n

Investment cost (MUSD)

Cumulative mitigation (MtCO2e)

Specific investment (MUSD/MtCO2e)

10.3

3.6

2.8

21.5 58.4

42.0 19.4

0.5 3.0

270.6

84.3

3.2

162.4

23

7.0

228.8

35.0

6.5

364.6

100.1

3.6

1190.2

84.2

14.1

1060.4

32.1

33.0

2312.6

354.5

6.5

7522.6

278.3

27.0

Includes replacements.

near to zero: efficient charcoal kilns and co-combustion of wood with coal. With the exception of palm oil biodiesel, liquid biofuel options show positive and high mitigation costs, ranging from 15 to 27 USD/tCO2e. Charcoal for pig-iron industry results with the largest mitigation cost (31.5 USD/tCO2e). Fig. 3 depicts the curve of cumulative mitigation as a function of unit cost. The options with negative costs accumulate nearly half of the total potential for emission reductions (around 500 MtCO2e).

Table 5 lists the options according to their total investment costs, and shows also the accumulated mitigation and specific investment. The options demanding very high capital investments are “Electricity from fuelwood” and “Sugarcane Ethanol”. Together, they account for more than one half of the mitigation potential, but require high specific investment (27 and 6.5 USD/tCO2e). There are three options of low investment (below 60 MUSD); of these two also show negative or very low mitigation costs (Co-combustion and Efficient charcoal kilns). Other intermediate options, including “Biodiesel J. curcas”, “Efficient Cook stoves”, “Biodiesel from Palm Oil” and “Sorghum Ethanol” require investments between 163 and 1190 MUSD each, and have intermediate specific costs.

4. Discussion When considering sustainability criteria for bioenergy in Mexico, the main differences between this and other studies are the fact that here we employ stricter criteria regarding the areas suitable for wood energy plantations, the availability of wood from native forests and potential cropping area for expansion for liquid biofuel production. The potential for biomass production calculated in this study falls within the lower limits estimated in [26]. Differences in specific sources in the previous study are due to the higher estimates of forest plantations (450–1246 PJ/yr); our lower estimate for biomass from native forest was due to the area that we assume available for sustainable forest management (26 Mha); and our higher estimate of ethanol and biodiesel potential, which were based on new cropping areas. In our study we also found lower values for residual biomass production from forest industries. According to our estimates, energy plantation areas would be 11 Mha, equivalent to 5.6% of Mexico’s land area and less than one half of the presently cropped area (24 Mha in 2010). About 60% of total mitigation potential is produced by only two options:

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sugarcane ethanol and electricity from fuelwood, which also have the higher potential for substitution of fossil fuels. Estimates of GHG mitigation that can be achieved with liquid biofuels should be taken with care as they do not include all emissions in the life cycle. Studies on emissions about the life cycle of ethanol production from sugarcane in Brazil reported between 21.3 g CO2e/MJ [34] to 45 g CO2e/MJ [35]. These emissions are even higher when considering those associated with land use land cover change (LULCC), adding about 14 gCO2e/MJ [36] to 46 gCO2e/ MJ [37]. To our knowledge, there is only one study in Mexico using Life Cycle Assessment (LCA) to assess GHG emissions from liquid biofuels [38]. The study reports that emissions from the production of ethanol from sugarcane would be about 37 gCO2e/MJ without emissions from LULCC, and up to 70 gCO2e/MJ when including conversion to sugarcane from tropical dry forests and pasturelands. When using these values, the mitigation potential of sugarcane is very significantly reduced. In the case of biodiesel from palm oil (for which there are no published values for Mexico), studies indicate GHG emissions in the life cycle of about 25 gCO2e/MJ without LULCC and up to 39 gCO2e/ MJ (i.e. a carbon sink) when plantations are established on pasturelands [39]. For the case of grain sorghum it is expected that the mitigation potential would be less then sugarcane ethanol and biodiesel from palm while J. curcas would have mixed results. This is because mitigation values as compared to fossil fuels varies from 9 to 29% for sorghum ethanol [40] and 30 to 80% for biodiesel from J. curcas (excluding emissions from LULCC) [41]. On the other hand, options using solid biomass, especially from native forests or residues, avoid land use changes and need much less fossil energy input because they do not require fertilizers, pesticides and other energy inputs (for example extra diesel use for tillage); it is thus very probable that their LCA emissions are much lower than those reported for biomass crops in international studies [22]. It is then important to conduct studies on the life cycle of fossil fuels versus bioenergy options in Mexico, mainly involving options for liquid biofuels. These studies should share a common methodology and set of assumptions, as LCA results vary greatly depending on considerations such as system boundaries, functional unit, treatment of co-products, emissions by LULCC, among others [42,43]. The option “Wood Pellets for Industrial” has a special significance because it may replace all the fuel oil and most of the diesel oil currently used by the Mexican industries. “Efficient Cook stoves” is also a very interesting option, because of its economic performance and associated health and social benefits [44]. Its main mitigation effect is due to the CH4 emissions because of more complete combustion. The options requiring low capital investment and showing negative mitigation costs have positive cash flows and may be financially self-sufficient. Thus, these should be easier to implement.

5. Conclusions There are a number of commercially available technological options for using biomass that have potential to mitigate greenhouse gases through fossil fuel substitution and increased efficiency, and which may be considered sustainable in other ways too. Some of these options even have negative abatement and investment costs, which in theory makes them prime candidates for immediate implementation. Our analysis suggests that this is the case for efficient wood-burning stoves, efficient kilns for charcoal production, and pellets to replace fuel oil and diesel.

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Mitigation potential and profitability of these bioenergy options in particular means that biomass can be considered as an important short-term energy source for greenhouse gas mitigation and energy transition policies. It is clear that large oil and gas companies, when attempting to diversify and reach out to more renewable energy solutions, tend to gravitate towards technologies that require the kinds of engineering and manufacturing approaches to which such companies are accustomed, and although it should be mentioned that the public petroleum company (PEMEX) has experimented with ethanol as gasoline substitute, CFE has shown very little interest in biomass alternatives despite the high mitigation potential that we identified here. The production and use of biomass requires a completely different kind of organization, it will be much more diffuse geographically and it will involve totally different kinds of production relationships, and probably much smaller companies to promote it. Capital may be hard to obtain for such companies to get started. To unleash the potential of biomass for power generation and mitigation of greenhouse gases will require specific public policies to make the electricity price from this source competitive. We would caution also that more research is definitely needed to complement a study such as we have presented here, to account for greenhouse gas emissions originating in the production, transformation and transportation of biomass. This is a major limitation of the present study. What we have reported is gross mitigation, which is usually lower than the net or effective mitigation, particularly in the case of agriculturally based options, such as liquid biofuels.

Acknowledgements This study was supported by the projects Fondo Sectorial CONACYT-SENER-Sustentabilidad Energetica no. 117808, the Fondo Sectorial CONACYT-SEDESOL no. 119143, and by Project PAPIIT-UNAM no IT 101512. We also thank to Maria de Jesús Pérez Orozco and Genice Grande for their help with data collection.

Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.rser.2014.11.062. References [1] [2] [3] [4]

[5]

[6] [7]

[8] [9] [10]

[11]

[12]

SENER. Balance Nacional de Energía 2010, México; 2011. World Bank. GDP ranking; 2013. SENER. Sistema de Información Energética; 2012. del Río F, Magar R. La encrucijada de la energía.1El pico del petróleo. In: Flores Valdés J, editor. Panorama Energético de México: Reflexiones académicas independientes. Mexico, DF: Secretaría Ejecutiva del Consejo Consultivo de Ciencias; 2011. p. 19–37. Vello K, Scott S, Tyler VL, Keith M. World shale gas resources: an initial assessment of 14 regions outside the united states. In: Energy USEIAUSDo, editor. Washington DC; 2011. SENER. Estrategia Nacional de Energía 2012–2026, Mexico; 2012. Alemán-Nava GS, Casiano-Flores VH, Cárdenas-Chávez DL, Díaz-Chavez R, Scarlat N, Mahlknecht J, et al. Renewable energy research progress in Mexico: a review. Renewable Sustainable Energy Rev 2014;32:140–53. SENER. Estrategia Nacional de Energía 2013–2027, Mexico; 2013. Gobernación Sd. Diario Oficial de la Federación. Ley General de Cambio Climático, Mexico; 2012. p. 44. Masera O, Aguillón J, Arvizu JL, Berrueta VM, Best G, De Buen O, et al. La Bioenergía en México. Un catalizador para el Desarrollo Sustentable. Mexico: Grupo Mundi-Prensa; 2006. Vargas-Moreno JM, Callejón-Ferre AJ, Pérez-Alonso J, Velázquez-Martí B. A review of the mathematical models for predicting the heating value of biomass materials. Renewable Sustainable Energy Rev 2012;16:3065–83. Koçar G, Civaş N. An overview of biofuels from energy crops: current status and future prospects. Renewable Sustainable Energy Rev 2013;28:900–16.

552

C.A. García et al. / Renewable and Sustainable Energy Reviews 43 (2015) 545–552

[13] Hirasawa T, Ookawa T, Kawai S, Funada R, Kajita S. Chapter 4—production technology for bioenergy crops and trees. In: Tojo S, Hirasawa T, editors. Research approaches to sustainable biomass systems. Boston, MA: Academic Press; 2014. p. 51–106. [14] Pedroli B, Elbersen B, Frederiksen P, Grandin U, Heikkilä R, Krogh PH, et al. Is energy cropping in Europe compatible with biodiversity? Opportunities and threats to biodiversity from land-based production of biomass for bioenergy purposes Biomass Bioenergy 2013;55:73–86. [15] Muller A. Chapter 23—sustainable farming of bioenergy crops. In: Gupta VK, Tuohy MG, Kubicek CP, Saddler J, Xu F, editors. Bioenergy research: advances and applications. Amsterdam: Elsevier; 2014. p. 407–17. [16] McBride AC, Dale VH, Baskaran LM, Downing ME, Eaton LM, Efroymson RA, et al. Indicators to support environmental sustainability of bioenergy systems. Ecol Indic 2011;11:1277–89. [17] Fargione J, Hill J, Tilman D, Polasky S, Hawthorne P. Land clearing and the biofuel carbon debt. Science 2008;319:1235–8. [18] Creutzig F, Popp A, Plevin R, Luderer G, Minx J, Edenhofer O. Reconciling topdown and bottom-up modelling on future bioenergy deployment. Nat Clim Change 2012;2:320–7. [19] Acreche MM, Valeiro AH. Greenhouse gasses emissions and energy balances of a non-vertically integrated sugar and ethanol supply chain: a case study in Argentina. Energy 2013;54:146–54. [20] Jordan N, Boody G, Broussard W, Glover JD, Keeney D, McCown BH, et al. Sustainable development of the agricultural bio-economy. Science 2007;316:1570–1. [21] Fingerman KR, Berndes G, Orr S, Richter BD, Vugteveen P. Impact assessment at the bioenergy-water nexus. Biofuels Bioprod Biorefin 2011;5:375–86. [22] Chum H, Faaij A, Moreira J, Berndes G, Dhamija P, Dong H, et al. Bioenergy. In: Edenhofer O, Pichs-Madruga R, Sokona Y, Seyboth K, Matschoss P, Kadner S, et al., editors. IPCC special report on renewable energy sources and climate change mitigation. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press; 2011. [23] Tilman D, Socolow R, Foley JA, Hill J, Larson E, Lynd L, et al. Beneficial biofuels —the food, energy, and environment trilemma. Science 2009;325:270–1. [24] McDowall W, Anandarajah G, Dodds PE, Tomei J. Implications of sustainability constraints on UK bioenergy development: assessing optimistic and precautionary approaches with UK MARKAL. Energy Policy 2012;47:424–36. [25] Jablonski S, Strachan N, Brand C, Bauen A. The role of bioenergy in the UK’s energy future formulation and modelling of long-term UK bioenergy scenarios. Energy Policy 2010;38:5799–816. [26] Islas J, Manzini F, Masera O. A prospective study of bioenergy use in Mexico. Energy 2007;32:2306–20. [27] Cornelissen S, Koper M, Deng YY. The role of bioenergy in a fully sustainable global energy system. Biomass Bioenergy 2012;41:21–33.

[28] Gonzalez-Salazar MA, Morini M, Pinelli M, Spina PR, Venturini M, Finkenrath M, et al. Methodology for biomass energy potential estimation: projections of future potential in Colombia. Renewable Energy 2014;69:488–505. [29] (CONABIO) CNpeCyeUdlB. Base de Datos Geográfica de Áreas Naturales Protegidas Estatales y del Distrito Federal de México, 2009; 2010. [30] U.S. EIA. Annual energy outlook 2010. U.S. Department of Energy; 2010. [31] CFE. Costos y Parámetros de Referencia para la Formulación de Proyectos de Inversión, Generación, Mexico; 2010. [32] US EIA. Electric power monthly; 2011. [33] US EIA. Natural gas navigator; 2011. [34] Seabra JEA, Macedo IC, Chum HL, Faroni CE, Sarto CA. Life cycle assessment of Brazilian sugarcane products: GHG emissions and energy use. Biofuels Bioprod Biorefin 2011;5:519–32. [35] Michael W, Jeongwoo H, Jennifer BD, Hao C, Amgad E. Well-to-wheels energy use and greenhouse gas emissions of ethanol from corn, sugarcane and cellulosic biomass for US use. Environ Res Lett 2012:7. [36] Laborde D. Assessing the land use change consequences of EuropeanBiofuel Policies. International Food Policy Istitute (IFPRI; 2011. [37] Khatiwada D, Seabra J, Silveira S, Walter A. Power generation from sugarcane biomass—a complementary option to hydroelectricity in Nepal and Brazil. Energy 2012;48:241–54. [38] García CA, Fuentes A, Hennecke A, Riegelhaupt E, Manzini F, Masera O. Lifecycle greenhouse gas emissions and energy balances of sugarcane ethanol production in Mexico. Appl Energy 2011;88:2088–97. [39] Uusitalo V, Väisänen S, Havukainen J, Havukainen M, Soukka R, Luoranen M. Carbon footprint of renewable diesel from palm oil, jatropha oil and rapeseed oil. Renewable Energy 2014;69:103–13. [40] Cai H, Dunn JB, Wang Z, Han J, Wang MQ. Life-cycle energy use and greenhouse gas emissions of production of bioethanol from sorghum in the United States. Biotechnol Biofuels 2013;6:141. [41] Kumar S, Singh J, Nanoti SM, Garg MO. A comprehensive life cycle assessment (LCA) of Jatropha biodiesel production in India. Bioresour Technol 2012;110: 723–9. [42] Khatiwada D, Seabra J, Silveira S, Walter A. Accounting greenhouse gas emissions in the lifecycle of Brazilian sugarcane bioethanol: methodological references in European and American regulations. Energy Policy 2012;47: 384–97. [43] Cherubini F, Strømman AH. Life cycle assessment of bioenergy systems: State of the art and future challenges. Bioresour Technol 2011;102:437–51. [44] García-Frapolli E, Schilmann A, Berrueta VM, Riojas-Rodríguez H, Edwards RD, Johnson M, et al. Beyond fuelwood savings: valuing the economic benefits of introducing improved biomass cookstoves in the Purépecha region of Mexico. Ecol Econ 2010;69:2598–605.