System expansion for handling co-products in LCA of sugar cane bio-energy systems: GHG consequences of using molasses for ethanol production

This study aims to establish a procedure for handling co-products in life cycle assessment (LCA) of a typical sugar cane system. The procedure is essential for environmental assessment of ethanol from molasses, a co-product of sugar which has long been used mainly for feed. We compare system expansion and two allocation procedures for estimating greenhouse gas (GHG) emissions of molasses ethanol. As seen from our results, system expansion yields the highest estimate among the three. However, no matter which procedure is used, a significant reduction of emissions from the fuel stage in the abatement scenario, which assumes implementation of substituting bioenergy for fossil-based energy to reduce GHG emissions, combined with a negligible level of emissions from the use stage, keeps the estimate of ethanol life cycle GHG emissions below that of gasoline. Pointing out that indirect land use change (ILUC) is a consequence of diverting molasses from feed to fuel, system expansion is the most adequate method when the purpose of the LCA is to support decision makers in weighing the options and consequences. As shown in the sensitivity analysis, an addition of carbon emissions from ILUC worsens the GHG balance of ethanol, with deforestation being a worst-case scenario where the fuel is no longer a net carbon saver but carbon emitter.     

CO2 gasification of dairy and swine manure: A life cycle assessment approach

CO₂ gasification of three different chars obtained from the pyrolysis of two dairy manure samples and a swine manure sample was evaluated. Dairy samples were firstly pretreated by anaerobic digestion process and swine sample by bio-drying process. Subsequently, manure samples were pyrolyzed between 30 °C and 980 °C obtaining a solid fuel (biochar), which was later gasified using different vol.% CO₂ (15–90%) which was the gasifying agent. Gasification was conducted at 900 °C. Thermal behavior and gasification characteristics were studied by means of the thermogravimetric-mass spectrometric analysis. In this sense, the reactivity of the samples was influenced by the catalytic activity of the mineral matter contained in the remaining biomass ashes. On the other hand, the viability of the manure gasification process vs the traditional use of manure as fertilizer was studied by means of the life cycle assessment (LCA) methodology. Two different scenarios were analyzed: gasification of manure sample before anaerobic digestion (Pre) and gasification of manure after anaerobic digestion (Dig R). According to the results obtained, the gasification of char Pre was the most viable scenario from the economic and environmental viewpoints whereas the gasification of char Dig R was the best energetic option.     

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.     

Fossil energy and GHG saving potentials of pig farming in the EU

In Europe, the highly developed livestock industry places a high burden on resource use and environmental quality. This paper examines pig meat production in North-West Europe as a base case and runs different scenarios to investigate how improvements in terms of energy and greenhouse gas (GHG) savings can be feasibly achieved. As shown in the results of the analysis, pig farming in the EU has a high potential to reduce fossil energy use and GHG emissions by taking improvement measures in three aspects: (i) feed use; (ii) manure management; and (iii) manure utilization. In particular, a combination of improvements in all mentioned aspects offers the highest savings potential of up to 61% fossil energy and 49% GHG emissions. In weighing these three aspects, manure utilization for energy production is found to be the most important factor in reducing fossil energy use and GHG emissions. However, when GHG implications of land use change and land opportunity cost associated with the production of feed crops (e.g. soy meal, cereals) are considered, reducing feed use becomes the main factor in improving GHG performance of EU pork.     

Life cycle assessment of olive pomace gasification for an up-draft fixed bed gasifier system

Biomass gasification has been considered as an important renewable energy alternative to deal with the environmental problems originating from fossil fuels and climate change effects. Olive pomace as a by-product of the olive oil production process is a significant biomass source. Although gasification technology is accepted as an environmentally friendly power system, the studies to determine its environmental impact via Life Cycle Assessment (LCA) are very limited. LCA is a key tool to evaluate all environmental impacts from the beginning to the end of the process. The aim of this study is to assess the overall environmental impacts of the olive pomace gasification for electricity generation and evaluation of its solid by-products namely biochar and tar. Four scenarios were compared to estimate the environmental impacts of gasification by-products with a LCA approach, following to the cradle-to-grave approach. The production of olive, olive pomace generation during its processing for olive oil production, gasification of olive pomace, construction of the gasifier, gas cleaning system and syngas composition have been included in the evaluations. It is clear from the analysis results that the scenarios have very low impact values in the case of beneficial usage of biochar in different industries. In terms of ozone layer depletion potential (2.74 × 10 ⁻⁶ kg CFC11 eq) and global warming potential (36.99 GWP100a), the paramount scenario from an environmental viewpoint is the scenario having the biochar and tar usage as a resource in another industry.     

Greenhouse gas impacts of ethanol from Iowa corn: Life cycle assessment versus system wide approach

Life cycle assessment (LCA) is the standard approach used to evaluate the greenhouse gas (GHG) benefits of biofuels. However, the need for the appropriate use of LCA in policy contexts is highlighted by recent findings that corn-based ethanol may actually increase GHG emissions. This is in contrary to most existing LCA results. LCA estimates can vary across studies due to heterogeneities in inputs and production technology. Whether marginal or average impacts are considered can matter as well. Most important of all, LCA is product-centered. The determination of the impact of biofuels expansion requires a system wide approach (SWA) that accounts for impacts on all affected products and processes.This paper presents both LCA and SWA for ethanol based on Iowa corn. LCA was conducted in several different ways. Growing corn in rotation with soybean generates 35% less GHG emissions than growing corn after corn. Based on average corn production, ethanol's GHG benefits were lower in 2007 than in 2006 because of an increase in continuous corn in 2007. When only additional corn was considered, ethanol emitted about 22% less GHGs than gasoline. SWA was applied to two simple cases. Using 2006 as a baseline and 2007 as a scenario, corn ethanol's benefits were about 20% of the emissions of gasoline. If geographical limits are expanded beyond Iowa, then corn ethanol could generate more GHG emissions than gasoline. These results highlight the importance of boundary definition for both LCA and SWA.     

Techno-economic analysis and life cycle assessment of hydrogen production from different biomass gasification processes

The paper presents techno-economic analyses and life cycle assessments (LCA) of the two major gasification processes for producing hydrogen from biomass: fluidized bed (FB) gasification, and entrained flow (EF) gasification. Results indicate that the thermal efficiency of the EF-based option (56%, LHV) is 11% higher than that of the FB-based option (45%), and the minimum hydrogen selling price of the FB-based option is $0.3 per kg H₂ lower than that of the EF-based option. When a carbon capture and liquefaction system is incorporated, the efficiencies of the EF- and FB-based processes decrease to 50% and 41%, respectively. The techno-economic analysis shows that at a biomass price of $100 per tonne, either a minimum price of $115/tonne CO_2e or a minimum natural gas price of $5/GJ is required to make the minimum hydrogen selling price of biomass-based plants equivalent to that of commercial natural gas-based steam methane reforming plants. Furthermore, the LCA shows that, biomass as a carbon-neutral feedstock, negative life cycle GHG emissions are achievable in all biomass-based options.     

Comparative life cycle assessment of hydrogen and other selected fuels

A streamlined life cycle assessment (LCA) is reported of a nuclear-based copper–chlorine (Cu–Cl) hydrogen production cycle, including estimates of fossil fuel energy use and greenhouse gas (GHG) emissions. Calculations revealed that the process requires 474 kJ of fossil fuel energy per MJ of hydrogen, which is less than for other hydrogen production processes. Moreover, GHG emissions are estimated to be 27 gCO₂e per MJ of hydrogen, which is only slightly higher than the corresponding value for wind-based hydrogen production. A sensitivity analysis demonstrated that the performance of the system could be further improved at higher yields of hydrogen. Although the system significantly outperformed fossil-based gasoline and hydrogen production pathways, the integrated nuclear and thermochemical cycle still requires significant research and development before commercialization is possible.     

Life cycle GHG assessment of fossil fuel power plants with carbon capture and storage

The evaluation of life cycle greenhouse gas emissions from power generation with carbon capture and storage (CCS) is a critical factor in energy and policy analysis. The current paper examines life cycle emissions from three types of fossil-fuel-based power plants, namely supercritical pulverized coal (super-PC), natural gas combined cycle (NGCC) and integrated gasification combined cycle (IGCC), with and without CCS. Results show that, for a 90% CO₂ capture efficiency, life cycle GHG emissions are reduced by 75–84% depending on what technology is used. With GHG emissions less than 170 g/kWh, IGCC technology is found to be favorable to NGCC with CCS. Sensitivity analysis reveals that, for coal power plants, varying the CO₂ capture efficiency and the coal transport distance has a more pronounced effect on life cycle GHG emissions than changing the length of CO₂ transport pipeline. Finally, it is concluded from the current study that while the global warming potential is reduced when MEA-based CO₂ capture is employed, the increase in other air pollutants such as NO_x and NH₃ leads to higher eutrophication and acidification potentials.     

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.     

Reducing life cycle greenhouse gas emissions of corn ethanol by integrating biomass to produce heat and power at ethanol plants

A life-cycle assessment (LCA) of corn ethanol was conducted to determine the reduction in the life-cycle greenhouse gas (GHG) emissions for corn ethanol compared to gasoline by integrating biomass fuels to replace fossil fuels (natural gas and grid electricity) in a U.S. Midwest dry-grind corn ethanol plant producing 0.19 hm³ y⁻¹ of denatured ethanol. The biomass fuels studied are corn stover and ethanol co-products [dried distillers grains with solubles (DDGS), and syrup (solubles portion of DDGS)]. The biomass conversion technologies/systems considered are process heat (PH) only systems, combined heat and power (CHP) systems, and biomass integrated gasification combined cycle (BIGCC) systems. The life-cycle GHG emission reduction for corn ethanol compared to gasoline is 38.9% for PH with natural gas, 57.7% for PH with corn stover, 79.1% for CHP with corn stover, 78.2% for IGCC with natural gas, 119.0% for BIGCC with corn stover, and 111.4% for BIGCC with syrup and stover. These GHG emission estimates do not include indirect land use change effects. GHG emission reductions for CHP, IGCC, and BIGCC include power sent to the grid which replaces electricity from coal. BIGCC results in greater reductions in GHG emissions than IGCC with natural gas because biomass is substituted for fossil fuels. In addition, underground sequestration of CO₂ gas from the ethanol plant’s fermentation tank could further reduce the life-cycle GHG emission for corn ethanol by 32% compared to gasoline.     

GHG emissions and energy performance of offshore wind power

This paper presents specific life cycle GHG emissions from wind power generation from six different 5 MW offshore wind turbine conceptual designs. In addition, the energy performance, expressed by the energy indicators Energy Payback Ratio (EPR) Energy Payback Time (EPT), is calculated for each of the concepts.There are currently few LCA studies in existence which analyse offshore wind turbines with rated power as great as 5 MW. The results, therefore, give valuable additional environmental information concerning large offshore wind power. The resulting GHG emissions vary between 18 and 31.4 g CO₂-equivalents per kWh while the energy performance, assessed as EPR and EPT, varies between 7.5 and 12.9, and 1.6 and 2.7 years, respectively. The relatively large ranges in GHG emissions and energy performance are chiefly the result of the differing steel masses required for the analysed platforms. One major conclusion from this study is that specific platform/foundation steel masses are important for the overall GHG emissions relating to offshore wind power. Other parameters of importance when comparing the environmental performance of offshore wind concepts are the lifetime of the turbines, wind conditions, distance to shore, and installation and decommissioning activities.Even though the GHG emissions from wind power vary to a relatively large degree, wind power can fully compete with other low GHG emission electricity technologies, such as nuclear, photovoltaic and hydro power.     

Addressing uncertainty in life-cycle carbon intensity in a national low-carbon fuel standard

Policies formulated to reduce greenhouse gas (GHG) emissions, such as a low-carbon fuel standard, frequently rely on life-cycle assessment (LCA) to estimate emissions, but LCA results are often highly uncertain. This study develops life-cycle models that quantitatively and qualitatively describe the uncertainty and variability in GHG emissions for both fossil fuels and ethanol and examines mechanisms to reduce those uncertainties in the policy process. Uncertainty regarding emissions from gasoline is non-negligible, with an estimated 90% confidence interval ranging from 84 to 100 g CO₂e/MJ. Emissions from biofuels have greater uncertainty. The widths of the 90% confidence intervals for corn and switchgrass ethanol are estimated to be on the order of 100 g CO₂e/MJ, and removing emissions from indirect land use change still leaves significant remaining uncertainty. Though an opt-in policy mechanism can reduce some uncertainty by incentivizing producers to self-report fuel production parameters, some important parameters, such as land use change emissions and nitrogen volatilization, cannot be accurately measured and self-reported. Low-carbon fuel policies should explicitly acknowledge, quantify, and incorporate uncertainty in life cycle emissions in order to more effectively achieve emissions reductions. Two complementary ways to incorporate this uncertainty in low carbon fuel policy design are presented.     

Mitigation of greenhouse gas emissions by adopting anaerobic digestion technology on dairy,sow and pig farms in Finland

The impact of anaerobic digestion (AD) technology on mitigating greenhouse gas (GHG) emissions from manure management on typical dairy, sow and pig farms in Finland was compared. Firstly, the total annual GHG emissions from the farms were calculated using IPCC guidelines for a similar slurry type manure management system. Secondly, laboratory-scale experiments were conducted to estimate methane (CH₄) potentials and process parameters for semi-continuous digestion of manures. Finally, the obtained experimental data were used to evaluate the potential renewable energy production and subsequently, the possible GHG emissions that could be avoided through adoption of AD technology on the studied farms. Results showed that enteric fermentation (CH₄) and manure management (CH₄ and N₂O) accounted for 231.3, 32.3 and 18.3 Mg of CO₂ eq. yr^?1 on dairy, sow and pig farms, respectively. With the existing farm data and experimental methane yields, an estimated renewable energy of 115.2, 36.3 and 79.5 MWh of heat yr^?1 and 62.8, 21.8 and 47.7 MWh of electricity yr^?1 could be generated in a CHP plant on these farms respectively. The total GHG emissions that could be offset on the studied dairy cow, sow and pig farms were 177, 87.7 and 125.6 Mg of CO₂ eq. yr^?1, respectively. The impact of AD technology on mitigating GHG emissions was mainly through replaced fossil fuel consumption followed by reduced emissions due to reduced fertilizer use and production, and from manure management.     

Biomass from agriculture in small-scale combined heat and power plants - A comparative life cycle assessment

Biomass produced on farm land is a renewable fuel that can prove suitable for small-scale combined heat and power (CHP) plants in rural areas. However, it can still be questioned if biomass-based energy generation is a good environmental choice with regards to the impact on greenhouse gas emissions, and if there are negative consequences of using of agricultural land for other purposes than food production.In this study, a simplified life cycle assessment (LCA) was conducted over four scenarios for supply of the entire demand of power and heat of a rural village. Three of the scenarios are based on utilization of biomass in 100 kW (e) combined heat and power (CHP) systems and the fourth is based on fossil fuel in a large-scale plant. The biomass systems analyzed were based on 1) biogas production with ley as substrate and the biogas combusted in a microturbine, 2) gasification of willow chips and the product gas combusted in an IC-engine and 3) combustion of willow chips for a Stirling engine. The two first scenarios also require a straw boiler.The results show that the biomass-based scenarios reduce greenhouse gas emissions considerably compared to the scenario based on fossil fuel, but have higher acidifying emissions. Scenario 1 has by far the best performance with respect to global warming potential and the advantage of utilizing a byproduct and thus not occupying extra land. Scenario 2 and 3 require less primary energy and less fossil energy input than 1, but set-aside land for willow production must be available. The low electric efficiency of scenario 3 makes it an unsuitable option.     

Incorporating uncertainty analysis into life cycle estimates of greenhouse gas emissions from biomass production

Before further investments are made in utilizing biomass as a source of renewable energy, both policy makers and the energy industry need estimates of the net greenhouse gas (GHG) reductions expected from substituting biobased fuels for fossil fuels. Such GHG reductions depend greatly on how the biomass is cultivated, transported, processed, and converted into fuel or electricity. Any policy aiming to reduce GHGs with biomass-based energy must account for uncertainties in emissions at each stage of production, or else it risks yielding marginal reductions, if any, while potentially imposing great costs.This paper provides a framework for incorporating uncertainty analysis specifically into estimates of the life cycle GHG emissions from the production of biomass. We outline the sources of uncertainty, discuss the implications of uncertainty and variability on the limits of life cycle assessment (LCA) models, and provide a guide for practitioners to best practices in modeling these uncertainties. The suite of techniques described herein can be used to improve the understanding and the representation of the uncertainties associated with emissions estimates, thus enabling improved decision making with respect to the use of biomass for energy and fuel production.     

Life cycle assessment study of solar PV systems: An example of a 2.7 kWp distributed solar PV system in Singapore

In life cycle assessment (LCA) of solar PV systems, energy pay back time (EPBT) is the commonly used indicator to justify its primary energy use. However, EPBT is a function of competing energy sources with which electricity from solar PV is compared, and amount of electricity generated from the solar PV system which varies with local irradiation and ambient conditions. Therefore, it is more appropriate to use site-specific EPBT for major decision-making in power generation planning. LCA and life cycle cost analysis are performed for a distributed 2.7 kW_p grid-connected mono-crystalline solar PV system operating in Singapore. This paper presents various EPBT analyses of the solar PV system with reference to a fuel oil-fired steam turbine and their greenhouse gas (GHG) emissions and costs are also compared. The study reveals that GHG emission from electricity generation from the solar PV system is less than one-fourth that from an oil-fired steam turbine plant and one-half that from a gas-fired combined cycle plant. However, the cost of electricity is about five to seven times higher than that from the oil or gas fired power plant. The environmental uncertainties of the solar PV system are also critically reviewed and presented.     

Life cycle assessment of conventional and optimised Jatropha biodiesel fuels

The environmental benefits and energy savings of the production of Jatropha fuels and operation in a typical LPV in India were examined. A baseline scenario and alternative optimised routes were assessed, considering different pathways of energy recovery from Jatropha coproducts. The following impact categories were assessed: Non-Renewable Energy (NRE) consumption, Global Warming Potential (GWP), Terrestrial Acidification Potential (TAP) and Respiratory Inorganic Effects (RIE). At present, the life cycle impact of Jatropha production and use is competitive with conventional diesel in terms of NRE and GHG emissions; however it results in higher local environmental impacts (RIE and TAP categories). Under optimised farming and processing practices and recovery of Jatropha coproducts either via co-generation, gasification or FT-diesel synthesis routes, Jatropha fuels reduce the impact of NRE, GHG, and RIE. The energy recovery paths to generate surplus electricity through generation and gasification routes show a better performance than FT-diesel synthesis routes in terms of NRE and GWP impacts. Nevertheless, in terms of local air pollution indicators, the FT-diesel synthesis route reveals the lowest emissions.     

Life cycle assessment of hydrogen production from biomass gasification systems

In this study, a Life Cycle Assessment (LCA) of biomass-based hydrogen production is performed for a period from biomass production to the use of the produced hydrogen in Proton Exchange Membrane (PEM) fuel cell vehicles. The system considered is divided into three subsections as pre-treatment of biomass, hydrogen production plant and usage of hydrogen produced. Two different gasification systems, a Downdraft Gasifier (DG) and a Circulating Fluidized Bed Gasifier (CFBG), are considered and analyzed for hydrogen production using actual data taken from the literature. Fossil energy consumption rate and Green House Gas Emissions (GHG) are defined and indicated first. Next, the LCA results of DG and CFBG systems are compared for 1 MJ/s hydrogen production to compare with each other as well as with other hydrogen production systems. While the fossil energy consumption rate and emissions are calculated as 0.088 MJ/s and 6.27 CO₂ eqv. g/s in the DG system, they are 0.175 MJ/s and 17.13 CO₂ eqv. g/s in the CFBG system, respectively. The Coefficient of Hydrogen Production Performance (CHPP) (newly defined as a ratio of energy content of hydrogen produced from the system to the total energy content of fossil fuels used) of the CFBG and DG systems are then determined to be 5.71 and 11.36, respectively. Thus, the effects of some parameters, such as energy efficiency, ratio of cost of hydrogen, on natural gas and capital investments efficiency are investigated. Finally, the costs of GHG emissions reduction are calculated to be 0.0172 and 0.24 $/g for the DG and CFBG systems, respectively.     

Comparative analysis of environmental impacts of maize-biogas and photovoltaics on a land use basis

This study aims to stimulate the discussion on how to optimize a sustainable energy mix from an environmental perspective and how to apply existing renewable energy sources in the most efficient way. Ground-mounted photovoltaics (PV) and the maize-biogas-electricity route are compared with regard to their potential to mitigate environmental pressure, assuming that a given agricultural area is available for energy production. Existing life cycle assessment (LCA) studies are taken as a basis to analyse environmental impacts of those technologies in relation to conventional technology for power and heat generation. The life-cycle-wide mitigation potential per area used is calculated for the impact categories non-renewable energy input, green house gas (GHG) emissions, acidification and eutrophication. The environmental performance of each system depends on the scenario that is assumed for end energy use (electricity and heat supply have been contemplated). In all scenarios under consideration, PV turns out to be superior to biogas in almost all studied impact categories. Even when maize is used for electricity production in connection with very efficient heat usage, and reduced PV performance is assumed to account for intermittence, PV can still mitigate about four times the amount of green house gas emissions and non-renewable energy input compared to maize-biogas. Soil erosion, which can be entirely avoided with PV, exceeds soil renewal rates roughly 20-fold on maize fields. Regarding the overall Eco-indicator 99 (H) score under most favourable assumptions for the maize-biogas route, PV has still a more than 100% higher potential to mitigate environmental burden. At present, the key advantages of biogas are its price and its availability without intermittence. In the long run, and with respect to more efficient land use, biogas might preferably be produced from organic waste or manure, whereas PV should be integrated into buildings and infrastructures.