Greenhouse gas emissions and energy balances of jatropha biodiesel as an alternative fuel in Tanzania

This paper evaluates GHG emissions and energy balances (i.e. net energy value (NEV), net renewable energy value (NREV) and net energy ratio (NER)) of jatropha biodiesel as an alternative fuel in Tanzania by using life cycle assessment (LCA) approach. The functional unit (FU) was defined as 1 tonne (t) of combusted jatropha biodiesel. The findings of the study prove wrong the notion that biofuels are carbon neutral, thus can mitigate climate change. A net GHG equivalent emission of about 848 kg t⁻¹ was observed. The processes which account significantly to GHG emissions are the end use of biodiesel (about 82%) followed by farming of jatropha for about 13%. Sensitivity analysis indicates that replacing diesel with biodiesel in irrigation of jatropha farms decreases the net GHG emissions by 7.7% while avoiding irrigation may reduce net GHG emissions by 12%. About 22.0 GJ of energy is consumed to produce 1 t of biodiesel. Biodiesel conversion found to be a major energy consuming process (about 64.7%) followed by jatropha farming for about 30.4% of total energy. The NEV is 19.2 GJ t⁻¹, indicating significant energy gain of jatropha biodiesel. The NREV is 23.1 GJ t⁻¹ while NER is 2.3; the two values indicate that large amount of fossil energy is used to produce biodiesel. The results of the study are meant to inform stakeholders and policy makers in the bioenergy sector.     

A comparison of avoided greenhouse gas emissions when using different kinds of wood energy

In this study, micro-level data from wood energy producers in Hedmark County were gathered and analysed. The aim was to find how much greenhouse gas (GHG) emissions various kinds of wood energy cause (not only CO₂, but also CH₄ and N₂O), which energy they substitute, their potential to reduce GHG emissions, and the major sources of uncertainty. The method was life cycle assessment. Six types of wood energy were studied: fuel wood, sawdust, pellets, briquettes, demolition wood, and bark.GHG emissions over the life cycle of the wood energy types in this study are 2–19% of the emissions from a comparable source of energy. The lowest figure is for demolition wood substituting oil in large combustion facilities, the highest for fuel wood used in dwellings to substitute electricity produced by coal-based power plants.Avoided GHG emissions per m³ wood used for energy were from 0.210 to 0.640 tonne CO₂-equivalents. Related to GWh energy produced, avoided GHG emissions were from 250 to 360 tonne CO₂-equivalents. Avoided GHG emissions per tonne CO₂ in the wood are 0.28–0.70 tonne CO₂-equivalents. The most important factors were technology used for combustion, which energy that is substituted, densities, and heating values. Inputs concerning harvest, transport, and production of the wood energy are not important.Overall, taking the uncertainties into account there is not much difference in avoided GHG emissions for the different kinds of wood energy.     

An energy evaluation of coupling nutrient removal from wastewater with algal biomass production

Recently, several life cycle analyses of algal biodiesel from virtual production facilities have outlined the potential environmental benefits and energetic balance of the process. There are a wide range of assumptions that have been utilized for these calculations, including the addition of fertilizers and carbon dioxide to achieve high algal yields in open ponds. This paper presents an energy balance of microalgal production in open ponds coupled with nutrient removal from wastewater. Actual microalgal yields and nutrient removal rates were obtained from four pilot-scale reactors (2500 gallons each) fed with wastewater effluent from a conventional activated sludge process for 6 months, and the data was used to estimate an energy balance for treating the total average 12 million gallons per day processed by the wastewater treatment plant. Since one of the most energy-intensive steps is the dewatering of algal cultures, several thickening and dewatering processes were compared. This analysis also includes the energy offset from removing nutrients with algal reactors rather than the biological nutrient removal processes typically utilized in municipal wastewater treatment. The results show that biofuel production is energetically favorable for open pond reactors utilizing wastewater as a nutrient source, even without an energy credit for nutrient removal. The energy content of algal biomass was also considered as an alternate to lipid extraction and biodiesel production. Direct combustion of algal biomass may be a more viable energy source than biofuel production, especially when the lipid content of dry biomass (10% in this field experiment) is lower than the high values reported in lab-scale reactors (50–60%).     

Life cycle GHG emissions from Malaysian oil palm bioenergy development: The impact on transportation sector's energy security

Malaysia's transportation sector accounts for 41% of the country's total energy use. The country is expected to become a net oil importer by the year 2011. To encourage renewable energy development and relieve the country's emerging oil dependence, in 2006 the government mandated blending 5% palm-oil biodiesel in petroleum diesel. Malaysia produced 16 million tonnes of palm oil in 2007, mainly for food use. This paper addresses maximizing bioenergy use from oil-palm to support Malaysia's energy initiative while minimizing greenhouse-gas emissions from land-use change. When converting primary and secondary forests to oil-palm plantations between 270–530 and 120–190 g CO₂-equivalent per MJ of biodiesel produced, respectively, is released. However, converting degraded lands results in the capture of between 23 and 85 g CO₂-equivalent per MJ of biodiesel produced. Using various combinations of land types, Malaysia could meet the 5% biodiesel target with a net GHG savings of about 1.03 million tonnes (4.9% of the transportation sector's diesel emissions) when accounting for the emissions savings from the diesel fuel displaced. These findings are used to recommend policies for mitigating GHG emissions impacts from the growth of palm oil use in the transportation sector.     

Energy efficiency and carbon dioxide emissions reduction opportunities in the US iron and steel sector

This article presents an in-depth analysis of cost-effective energy efficiency and carbon dioxide emissions reduction opportunities in the US iron and steel industry. We show that physical energy intensity for iron and steelmaking (at the aggregate level, standard Industrial Classification 331, 332) dropped 27%, from 35.6 GJ/tonne to 25.9 GJ/tonne between 1958 and 1994, while carbon dioxide intensity (carbon dioxide emissions expressed in tonnes of carbon per tonne of steel) dropped 39%. We provide a baseline for 1994 energy use and carbon dioxide emissions from US blast furnaces and steel mills (SIC 3312) disaggregated by the processes used in steelmaking. Energy-efficient practices and technologies are identified and analyzed for each of these processes. Examination of 47 specific energy efficiency technologies and measures found a total cost-effective reduction potential of 3.8 GJ/t, having a payback period of three years or less. This is equivalent to a potential energy efficiency improvement of 18% of 1994 US iron and steel energy use and is roughly equivalent to 19% reduction of 1994 US iron and steel carbon dioxide emissions. The measures have been ranked in a bottom-up energy conservation supply-curve.     

Market penetration of biodiesel

This research examines in detail the technology and economics of substituting biodiesel for diesel #2. This endeavor examines three areas. First, the benefits of biodiesel are examined, and the technical problems of large-scale implementation. Second, the biodiesel production possibilities are examined for soybean oil, corn oil, tallow, and yellow grease, which are the largest sources of feedstocks for the United States. Examining in detail the production possibilities allows to identity the extent of technological change, production costs, byproducts, and greenhouse gas (GHG) emissions. Finally, a U.S. agricultural model, FASOMGHG was used to predict market penetration of biodiesel, given technological progress, variety of technologies and feedstocks, market interactions, energy prices, and carbon dioxide equivalent prices.FASOMGHG has several interesting results. First, diesel fuel prices have an expansionary impact on the biodiesel industry. The higher the diesel fuel prices, the more biodiesel is produced. However, given the most favorable circumstances, the maximum biodiesel market penetration is 9% in 2030 with a wholesale diesel price of $4 per gallon. Second, the two dominant sources of biodiesel are from corn and soybeans. Sources like tallow and yellow grease are more limited, because they are byproducts of other industries. Third, GHG prices have an expansionary impact on the biodiesel prices, because biodiesel is quite GHG efficient. Finally, U.S. government subsidies on biofuels have an expansionary impact on biodiesel production, and increase market penetration at least an additional 3%.     

Potentials for energy efficiency improvement in the US cement industry

This paper reports on an in-depth analysis of the US cement industry, identifying cost-effective energy efficiency measures and potentials. Between 1970 and 1997, primary physical energy intensity for cement production (SIC 324) dropped 30%, from 7.9 GJ/t to 5.6 GJ/t, while specific carbon dioxide emissions due to fuel consumption and clinker calcination dropped 17%, from 0.29 tC/tonne to 0.24 tC/tonne. We examined 30 energy-efficient technologies and measures and estimated energy savings, carbon dioxide savings, investment costs, and operation and maintenance costs for each of the measures. We constructed an energy conservation supply curve for the US cement industry which found a total cost-effective energy saving of 11% of 1994 energy use for cement making and a saving of 5% of total 1994 carbon dioxide emissions. Assuming the increased production of blended cement, the technical potential for energy efficiency improvement would not change considerably. However, the cost-effective potential would increase to 18% of total energy use, and carbon dioxide emissions would be reduced by 16%. This demonstrates that the use of blended cements is a key cost-effective strategy for energy efficiency improvement and carbon dioxide emission reductions in the US cement industry.     

Effect of organic fraction of municipal solid waste addition to high rate activated sludge system for hydrogen production from carbon rich waste sludge

Municipal solid waste has been used for bio-methane production for many years. However, both methane and carbon dioxide that is produced during bio-methanization increases the greenhouse gas emissions; therefore, hydrogen production can be one of the alternatives for energy production from waste. Hydrogen production from the organic substance was studied in this study with the waste activated sludge from the municipal wastewater treatment. High rated activated sludge (HRAS) process was applied for the treatment to reduce energy consumption and enhance the organic composition of WAS. The highest COD removal (76%) occurred with the 12 g/L organic fraction of municipal solid waste (OFMSW) addition at a retention time of 120 min. The maximum hydrogen and methane yields for the WAS was 18.9 mL/g VS and 410 mL/g VS respectively. Total carbon emission per g VS of the substrate (OFMSW + waste activated sludge) was found as 0.087 mmol CO₂ and 28.16 mmol CO₂ for dark fermentation and bio-methanization respectively. These kinds of treatment technologies required for the wastewater treatment plantcompensate it some of the energy needs in a renewable source. In this way, the HRAS process decreases the energy requirement of wastewater treatment plant, and carbon-rich waste sludge enables green energy production via lower carbon emissions.     

High rate anaerobic digestion of wastewater separated from grease trap waste

The co-production of biodiesel and methane gas from grease trap waste (GTW) was evaluated and compared against theoretical predictions of methane production from sole anaerobic digestion of GTW. The GTW was first processed into two separate phases comprised of fats, oil, and grease (FOG) and high strength wastewater (GTW wastewater). The GTW wastewater was then anaerobically digested in biochar packed up-flow column reactors to produce methane gas and a low-strength wastewater effluent while the FOG phase was set aside for conversion into biodiesel. Anaerobic digestion efficiencies that yielded chemical oxygen demand (COD) reductions up to 95% and methane headspace concentrations between 60 and 80% were achieved along with FOG to biodiesel conversion efficiencies of 90%. Methane production yields (m³ per kg COD reduced) achieved theoretical maximums with near total depletion of the volatile organic acids. High resolution images of biochar samples confirmed extensive coverage with thick biofilm communities. Microbial analysis revealed broad spectrum populations of anaerobic bacteria that ferment organic substrates to produce acetate, ethanol, and hydrogen as major end products as well as archaeal populations that produce methane gas. Energy calculations validated the co-production of biodiesel and methane gas from GTW as a competitive option relative to its co-digestion with sewage sludge.     

Environmental and economic feasibility of sugarcane ethanol for the Mexican transport sector

This study analyzes the environmental and economic feasibility of ethanol produced from sugarcane for use as a potential gasoline substitute in the Mexican transport sector from 2010 to 2030. One scenario was created by projecting the historical trend of energy demand assuming that a fraction of this demand is satisfied with ethanol produced from the cultivation of 2.9 million hectares of sugarcane. A life cycle study was performed according to the recommendations from the European Union Directive on Renewable Energies (that include direct land use change emissions) and was used to estimate life cycle Greenhouse gas (GHG) emissions. The method used by Fingerman et al. (2010) was adopted to estimate the water consumption. In the economic analysis, the production cost of ethanol was calculated, and a mitigation cost for carbon dioxide equivalent emissions was estimated. The potential for employment generation was also estimated. The results demonstrate that water use increases by 29.4 times and that the costs increase by 10,706 million USD with the alternative scenario. This scenario, however, has the potential to create 560,619 direct jobs. Furthermore, GHG mitigation is confirmed since the reference scenario resulted in GHG gasoline life cycle emissions of 78.7 kgCO_2e/GJ while the alternative scenario resulted in Ethanol GHG emissions in the life cycle of 57.52 kgCO_2e/GJ.     

Improvement potential for net energy balance of biodiesel derived from palm oil: A case study from Indonesian practice

Biodiesel derived from palm oil has been recognized as a high-productivity oil crop among the first generation of biofuels. This study evaluated and discussed the net energy balance for biodiesel in Indonesia by calculating the net energy ratio (NER) and net energy production (NEP) form the total energy input and output. The results of the calculation of energy input for the default scenario demonstrated that the primary energy inputs in the biodiesel production lifecycle were the methanol feedstock, energy input during the biodiesel production process, and urea production. These three items amounted to 85% of the total energy input. Next, we considered and evaluated ways to potentially improve the energy balance by utilizing by-products and biogas from wastewater treatment in the palm oil mill. This result emphasized the importance of utilizing the biomass residue and by-products. Finally, we discussed the need to be aware of energy balance issues between countries when biofuels are transported internationally.     

GHG balance of crude palm oil for biodiesel production in the northern region of Brazil

Biomass has become important as an alternative to fossil fuels and as a means to decrease greenhouse gas (GHG) emissions, particularly in tropical regions such as Brazil. Therefore, the demand for energy crops has increased strongly, and among such crops, palm oil is distinctive because of its productivity and well-developed production techniques. This paper intends to evaluate crude palm oil's GHG balance through a life-cycle assessment approach. This study is based on the average data of an ideal palm oil system in the northern region of Brazil. In the production of crude palm oil, a large amount of CO₂ sequestration occurs during the growth of palm oil trees. In contrast, the greatest emissions are biotic CO₂, which returns to the atmosphere and emissions from fertilizer production. The GHG balance of an oil palm plantation is approximately −208 kg CO₂-equiv./1000 kg crude palm oil per year.     

The impact of the life cycle analysis methodology on whether biodiesel produced from residues can meet the EU sustainability criteria for biofuel facilities constructed after 2017

This paper considers biodiesel production from residues; tallow and used cooking oil (UCO). The tallow system is more complex involving two processes. The first process is rendering in which tallow (animal fat) and Meat and Bone Meal (MBM) are produced from the slaughter of cattle. MBM is assumed as a thermal energy source for cement manufacture and thus is not used for biodiesel production. The second process is biodiesel production from tallow. Three methodologies are employed to examine sustainability of the biodiesel. The no allocation approach assigns all the parasitic demands to the tallow; thus all energies required to make both MBM and tallow are associated with the tallow biodiesel. The resulting energy balance is negative. The substitution approach allocates the energy in MBM (used to produce cement) to tallow biodiesel. This results in the net energy being greater than the gross energy. The allocation by energy content method divides the parasitic demands of the rendering process between tallow and MBM by energy content. The parasitic demands of the biodiesel process are divided by energy content of the biodiesel, glycerol and K-fertiliser. For tallow biodiesel this yielded a net energy value of 38.6% of gross energy. The same method generated a net energy value of 67% for UCO biodiesel. More importantly the recommended method (allocation by energy content) generated a value of 54% greenhouse gas (GHG) emission savings for tallow and a value of 69% for UCO. Plants commencing after 2017, need to have a 60% GHG emission savings, to be considered sustainable. Thus a facility treating both feedstocks would need to treat a maximum of 60% tallow to be considered sustainable after 2017.     

Economic and environmental competitiveness of high temperature electrolysis for hydrogen production

Alternative hydrogen production technologies are sought in part to reduce the greenhouse gas (GHG) emissions intensity compared with Steam Methane Reforming (SMR), currently the most commonly employed hydrogen production technology globally. This study investigates hydrogen production via High Temperature Steam Electrolysis (HTSE) in terms of GHG emissions and cost of hydrogen production using a combination of Aspen HYSYS® modelling and life cycle assessment. Results show that HTSE yields life cycle GHG emissions from 3 to 20 kg CO_2e/kg H₂ and costs from $2.5 to 5/kg H₂, depending on the system parameters (e.g., energy source). A carbon price of $360/tonne CO_2e is estimated to be required to make HTSE economically competitive with SMR. This is estimated to potentially decrease to $50/tonne CO_2e with future technology advancements (e.g., fuel cell lifetime). The study offers insights for technology developers seeking to improve HTSE, and policy makers for decisions such as considering support for development of hydrogen production technologies.     

Greenhouse gas emissions and energy balance of palm oil biofuel

The search for alternatives to fossil fuels is boosting interest in biodiesel production. Among the crops used to produce biodiesel, palm trees stand out due to their high productivity and positive energy balance. This work assesses life cycle emissions and the energy balance of biodiesel production from palm oil in Brazil. The results are compared through a meta-analysis to previous published studies: Wood and Corley (1991) [Wood BJ, Corley RH. The energy balance of oil palm cultivation. In: PORIM intl. palm oil conference – agriculture; 1991.], Malaysia; Yusoff and Hansen (2005) [Yusoff S, Hansen SB. Feasibility study of performing an life cycle assessment on crude palm oil production in Malaysia. International Journal of Life Cycle Assessment 2007;12:50–8], Malaysia; Angarita et al. (2009) [Angarita EE, Lora EE, Costa RE, Torres EA. The energy balance in the palm oil-derived methyl ester (PME) life cycle for the cases in Brazil and Colombia. Renewable Energy 2009;34:2905–13], Colombia; Pleanjai and Gheewala (2009) [Pleanjai S, Gheewala SH. Full chain energy analysis of biodiesel production from palm oil in Thailand. Applied Energy 2009;86:S209–14], Thailand; and Yee et al. (2009) [Yee KF, Tan KT, Abdullah AZ, Lee KT. Life cycle assessment of palm biodiesel: revealing facts and benefits for sustainability. Applied Energy 2009;86:S189–96], Malaysia. In our study, data for the agricultural phase, transport, and energy content of the products and co-products were obtained from previous assessments done in Brazil. The energy intensities and greenhouse gas emission factors were obtained from the Simapro 7.1.8. software and other authors. These factors were applied to the inputs and outputs listed in the selected studies to render them comparable. The energy balance for our study was 1:5.37. In comparison the range for the other studies is between 1:3.40 and 1:7.78. Life cycle emissions determined in our assessment resulted in 1437 kg CO₂e/ha, while our analysis based on the information provided by other authors resulted in 2406 kg CO₂e/ha, on average. The Angarita et al. (2009) [Angarita EE, Lora EE, Costa RE, Torres EA. The energy balance in the palm oil-derived methyl ester (PME) life cycle for the cases in Brazil and Colombia. Renewable Energy 2009;34:2905–13] study does not report emissions. When compared to diesel on a energy basis, avoided emissions due to the use of biodiesel account for 80 g CO₂e/MJ. Thus, avoided life cycle emissions associated with the use of biodiesel yield a net reduction of greenhouse gas emissions. We also assessed the carbon balance between a palm tree plantation, including displaced emissions from diesel, and a natural ecosystem. Considering the carbon balance outcome plus life cycle emissions the payback time for a tropical forest is 39 years. The result published by Gibbs et al. (2008) [Gibbs HK, Johnston M, Foley JA, Holloway T, Monfreda C, Ramankutty N, et al., Carbon payback times for crop-based biofuel expansion in the tropics: the effects of changing yield and technology. Environmental Research Letters 2008;3:10], which ignores life cycle emissions, determined a payback range for biodiesel production between 30 and 120 years.     

Biodiesel production from oleaginous microorganisms

High energy prices, energy and environment security, concerns about petroleum supplies are drawing considerable attention to find a renewable biofuels. Biodiesel, a mixture of fatty acid methyl esters (FAMEs) derived from animal fats or vegetable oils, is rapidly moving towards the mainstream as an alternative source of energy. However, biodiesel derived from conventional petrol or from oilseeds or animal fat cannot meet realistic need, and can only be used for a small fraction of existing demand for transport fuels. In addition, expensive large acreages for sufficient production of oilseed crops or cost to feed animals are needed for raw oil production. Therefore, oleaginous microorganisms are available for substituting conventional oil in biodiesel production. Most of the oleaginous microorganisms like microalgae, bacillus, fungi and yeast are all available for biodiesel production. Regulation mechanism of oil accumulation in microorganism and approach of making microbial diesel economically competitive with petrodiesel are discussed in this review.     

Carbon emission as a function of energy generation in hydroelectric reservoirs in Brazilian dry tropical biome

Most energy generation globally is fueled by coal and oil, raising concerns about greenhouse gas emissions. Hydroelectric reservoirs are anthropogenic aquatic systems that occur across a wide geographical extent, and, in addition to their importance for energy production, they have the potential to release two important greenhouse gases (GHGs), carbon dioxide and methane. We report results from an extensive study of eight hydroelectric reservoirs located in central and southeastern tropical Brazil. In the Brazilian dry tropical biome reservoirs, emissions (in tons of CO₂ Eq. per MW h) varied from 0.01 to 0.55, and decreased with reservoir age. Total emissions were higher in the reservoir lake when compared to the river downstream the dam; however, emissions per unit area, in the first kilometer of the river after the dam, were higher than that in the reservoir. The results showed, despite higher carbon emissions per energy production in the youngest reservoirs, lower emission from hydroelectric reservoirs from the studied region in relation to thermo electrical supply, fueled by coal or fossil fuel. The ratio emission of GHG per MWh produced is an important parameter in evaluating the service provided by hydroelectric reservoir and for energy planning policies.     

The net greenhouse warming forcing of methanol produced from biomass

Recent national and international actions regarding atmosphere warming mitigation, clean technology, and technology transfer have emphasized the need for a method for unambiguous greenhouse gas emissions analysis for comparing technologies, documentation of application of the method, and proof of applicability. We have developed and applied such an approach to production of methanol fuel from woody biomass. The entire approach is detailed, whereby the system was defined, its emissions for its entire lifetime delineated, and the atmospheric warming forcing calculated for that lifetime plus after effects. The results are presented with material and energy balances including ancillary equipment, external energy subsidies and invested quantities. These extend the analysis considerably beyond those possible using the global warming potential (GWP). For wood input of 283 mg day⁻¹, 70 mg of methanol are produced. System carbon dioxide emissions are 3.18 tonne/tonne methanol produced, with another 1.37 mg emitted when that tonne methanol is burned in a vehicle. System energy usage efficiency was 41.2%, and 41.1% with inclusion of energy to construct the system. In essence, more than two Joules of carbon must be produced in wood for every Joule burned in the vehicle.     

Trade-linked Canada–United States household environmental impact analysis of energy use and greenhouse gas emissions

We compare energy use and greenhouse gas (GHG) emissions associated with total household expenditures and activities in Canada and US in 1997, the first detailed estimate of environmental burdens for Canadian households. We estimate direct burdens from published government data and indirect burdens using an industry-by-commodity, bi-national economic input–output life cycle assessment model developed in this study. Comparing 30 expenditure and two activity categories, per capita US household expenditures were 70% higher, while per capita household energy use and GHG emissions were only 10% and 44% higher, respectively. Energy use/dollar of expenditure was higher in most Canadian categories, while the average ratio of GHG emissions/energy use was higher in the US (65 vs 50 kg Eq. CO₂/GJ) due largely to a higher proportion of electricity from nonrenewable sources. Indirect environmental burdens represented 63–69% of total burdens and 62–70% of total burdens were associated with household operation and transportation. Key drivers of differences between energy profiles were: higher per capita electricity use by Canadian households, and higher US household private health care expenditures and motor fuel use. Energy-intensive production for export represented a higher proportion of Canadian production, resulting in less agreement between consumption and production-based analyses for Canada than US.     

Low carbon hydrogen production in Canada via natural gas pyrolysis

Large scale, low cost, and low carbon intensity hydrogen production is needed to reduce emissions in the energy and transportation sectors. We present a techno-economic analysis and life cycle assessment of natural gas pyrolysis technologies for hydrogen production, with carbon black (CB) as a co-product. Four designs were considered based on the source of heat to the pyrolysis system, the combustion medium, and use of carbon capture (CC) technology. The oxygen-fired-CB design with CC is the most attractive from financial and environmental perspectives, superior to a conventional steam methane reformer (SMR) process with CC. The estimated pre-tax minimum hydrogen selling prices for the pyrolysis technologies range between $1.08/kg and $2.43/kg when natural gas (NG) costs $3.76/GJ. Key advantages include near-zero onsite GHG emissions of the oxygen-fired-CB design with CC and up to 41% lower GHG emissions compared to the SMR + CC process. The results indicate that natural gas pyrolysis may be a feasible pathway for hydrogen production.