Life cycle assessment of greenhouse gas emissions of feedlot manure management practices: Land application versus gasification

Animal waste is an important source of anthropogenic GHG emissions, and in most cases, manure is managed by land application. Nevertheless, due to the huge amounts of manure produced annually, alternative manure management practices have been proposed, one of which is gasification, aimed to convert manure into clean energy-syngas. Syngas can be utilized to provide energy or power. At the same time, the byproduct of gasification, biochar, can be transported back to fields as a soil amendment. Environmental impacts are crucial in selecting the appropriate manure strategy. Therefore, GHG emissions during manure management systems (land application and gasification) were evaluated and compared by life cycle assessment (LCA) in our study. LCA is a universally accepted tool to determine GHG emissions associated with every stage of a system. Results showed that the net GHG emissions in land application scenario and gasification scenario were 119 and -643 kg CO₂-eq for one tonne of dry feedlot manure, respectively. Moreover, sensitive factors in the gasification scenario were efficiency of the biomass integrated gasification combined cycle (BIGCC) system and energy source of avoided electricity generation. Overall, due to the environmental effects of syngas and biochar, gasification of feedlot manure is a much more promising technique as a way to reduce GHG emissions than is land application.     

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.     

How certain are greenhouse gas reductions from bioenergy? Life cycle assessment and uncertainty analysis of wood pellet-to-electricity supply chains from forest residues

Climate change and energy policies often encourage bioenergy as a sustainable greenhouse gas (GHG) reduction option. Recent research has raised concerns about the climate change impacts of bioenergy as heterogeneous pathways of producing and converting biomass, indirect impacts, uncertainties within the bioenergy supply chains and evaluation methods generate large variation in emission profiles. This research examines the combustion of wood pellets from forest residues to generate electricity and considers uncertainties related to GHG emissions arising at different points within the supply chain. Different supply chain pathways were investigated by using life cycle assessment (LCA) to analyse the emissions and sensitivity analysis was used to identify the most significant factors influencing the overall GHG balance. The calculations showed in the best case results in GHG reductions of 83% compared to coal-fired electricity generation. When parameters such as different drying fuels, storage emission, dry matter losses and feedstock market changes were included the bioenergy emission profiles showed strong variation with up to 73% higher GHG emissions compared to coal. The impact of methane emissions during storage has shown to be particularly significant regarding uncertainty and increases in emissions. Investigation and management of losses and emissions during storage is therefore key to ensuring significant GHG reductions from biomass.     

Energy intensity and greenhouse gas emission of a purchase in the retail park service sector: An integrative approach

The aim of this paper is to describe the energetic metabolism of a retail park service system under an integrative approach. Energy flow accounting was applied to a case study retail park in Spain, representative of the sector across Europe, after redefining the functional unit to account for both direct energy use (buildings, gardens and outdoor lighting) and indirect energy use (employee and customer transportation). A life cycle assessment (LCA) was then undertaken to determine energy global warming potential (GWP) and some energy intensity and greenhouse gases (GHG) emission indicators were defined and applied. The results emphasise the importance of service systems in global warming policies, as a potential emission of 9.26 kg CO₂/purchase was obtained for the case study, relating to a consumption of 1.64 KOE of energy, of which 21.9% was spent on buildings and 57.9% on customer transportation. Some strategies to reduce these emissions were considered: increased supply, energy efficiency, changes in distribution of modes of transport, changes in location and changes in the mix of land uses. A combination of all of these elements in a new retail park could reduce GHG emissions by more than 50%, as it is planning strategies, which seem to be the most effective.     

Greenhouse gas reporting for biofuels: A comparison between the RED,RTFO and PAS2050 methodologies

Biofuels have been identified as a potential short-term solution for reducing greenhouse gas (GHG) emissions from road transport. Currently, ‘1st generation’ biofuels are produced from food crops, but there are concerns with the indirect effects of utilising edible crops for fuel. There is increased interest in producing ‘2nd generation’ biofuels from woody crops and straw, as these can be grown on lower grade land or do not compete directly with food. In order to ensure that biofuels actually deliver emission savings, the overall GHG balance of producing them must be calculated accurately, and compared with conventional fossil fuels. The GHG balance can vary significantly however, depending on biomass type, the production processes, the indirect effects, and also by the method by which the GHG emission balance is calculated. Currently, in the UK, there are three main GHG methodologies that potentially affect biofuel producers. Each has a different approach to measure GHG emissions from biofuel production, and each provides a different result, causing difficulties for policy makers. This study performs a partial life cycle assessment for bioethanol production from wheat grain and wheat straw to demonstrate the variability of the results between methodologies.     

Sustainable energy system design with distributed renewable resources considering economic,environmental and uncertainty aspects

Electricity generation using renewable energy generation technologies is one of the most practical alternatives for network planners in order to achieve national and international Greenhouse Gas (GHG) emission reduction targets. Renewable Distributed Generation (DG) based Hybrid Energy System (HES) is a sustainable solution for serving electricity demand with reduced GHG emissions. A multi-objective optimisation technique for minimising cost, GHG emissions and generation uncertainty has been proposed in this paper to design HES for sustainable power generation and distribution system planning while considering economic and environmental issues and uncertainty in power availability of renewable resources. Life cycle assessment has been carried out to estimate the global warming potential of the embodied GHG emissions from the electricity generation technologies. The uncertainty in the availability of renewable resources is modelled using the method of moments. A design procedure for building sustainable HES has been presented and the sensitivity analysis is conducted for determining the optimal solution set.     

Should Alberta upgrade oil sands bitumen? An integrated life cycle framework to evaluate energy systems investment tradeoffs

The inclusion of greenhouse gas (GHG) emissions costs in energy systems investment decision-making requires the development of a framework that accounts for GHG and economic tradeoffs. This paper develops such a framework by integrating partial cost–benefit analysis with life cycle assessment to explore the question of whether bitumen should be upgraded in the Canadian province of Alberta to produce synthetic crude oil (SCO), or blended with light hydrocarbons to produce lower-quality diluted bitumen (dilbit). The net present value (NPV) of these options is calculated from the stakeholder perspectives of the oil sands industry, the Alberta public, and a climate-concerned Alberta resident. This calculation includes monetized GHG emissions costs stemming from a hypothetical economy-wide GHG price, and a sensitivity analysis explores the effects of variations in technical and economic conditions on stakeholders’ preferences. We find that under most plausible sets of conditions, industry would prefer the dilution option, while the climate-concerned Alberta resident would prefer the upgrading option. In contrast, the preferences of the general Alberta public depend on the values of key variables (e.g., the SCO-dilbit price differential). Key drivers of differences among stakeholders’ preferences include different perceptions of risks and responsibilities for life cycle GHG emissions.     

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.     

Greenhouse gas emissions from electricity generated by offshore wind farms

For wind power generation offshore sites offer significantly better wind conditions compared to onshore. At the same time, the demand for raw materials and therefore the related environmental impacts increase due to technically more demanding wind energy converters and additional components (e.g. substructure) for the balance of plant. Additionally, due to environmental concerns offshore wind farms will be sited farshore (i.e. in deep water) in the future having a significant impact on the operation and maintenance efforts (O&M). Against this background the goal of this analysis is an assessment of the specific GHG (greenhouse gas) emissions as a function of the site conditions, the wind mill technology and the O&M necessities. Therefore, a representative offshore wind farm is defined and subjected to a detailed LCA (life cycle assessment). Based on parameter variations and modifications within the technical and logistical system, promising configurations regarding GHG emissions are determined for different site conditions. Results show, that all parameters related to the energy yield have a distinctive impact on the specific GHG emissions, whereas the distance to shore and the water depth affect the results marginally. By utilizing the given improvement potentials GHG emissions of electricity from offshore wind farms are comparable to those achieved onshore.     

Climate mitigation comparison of woody biomass systems with the inclusion of land-use in the reference fossil system

While issues of land-use have been considered in many direct analyses of biomass systems, little attention has heretofore been paid to land-use in reference fossil systems. Here we address this limitation by comparing forest biomass systems to reference fossil systems with explicit consideration of land-use in both systems. We estimate and compare the time profiles of greenhouse gas (GHG) emission and cumulative radiative forcing (CRF) of woody biomass systems and reference fossil systems. A life cycle perspective is used that includes all significant elements of both systems, including GHG emissions along the full material and energy chains. We consider the growth dynamics of forests under different management regimes, as well as energy and material substitution effects of harvested biomass. We determine the annual net emissions of CO₂, N₂O and CH₄ for each system over a 240-year period, and then calculate time profiles of CRF as a proxy measurement of climate change impact. The results show greatest potential for climate change mitigation when intensive forest management is applied in the woody biomass system. This methodological framework provides a tool to help determine optimal strategies for managing forests so as to minimize climate change impacts. The inclusion of land-use in the reference system improves the accuracy of quantitative projections of climate benefits of biomass-based systems.     

Blending blue hydrogen with natural gas for direct consumption: Examining the effect of hydrogen concentration on transportation and well-to-combustion greenhouse gas emissions

Jurisdictions are looking into mixing hydrogen into the natural gas (NG) system to reduce greenhouse gas (GHG) emissions. Earlier studies have focused on well-to-wheel analysis of H₂ fuel cell vehicles, using high-level estimates for transportation-based emissions. There is limited research on transportation emissions of hythane, a blend of H₂ and NG used for combustion. An in-depth analysis of the pipeline transportation system was performed for hythane and includes sensitivity and uncertainty analyses. When hythane with 15% H₂ is used, transportation GHG emissions (gCO2eq/GJ) increase by 8%, combustion GHG emissions (gCO2eq/GJ) decrease by 5%, and pipeline energy capacity (GJ/hr) decreases by 11% for 50–100 million m³/d pipelines. Well-to-combustion (WTC) emissions increase by 2.0% without CCS, stay the same with a 41% CCS rate, decrease by 2.8% for the 100% CCS scenario, and decrease by 3.6% in the optimal CO₂-free scenario. While hythane contains 15% H₂ by volume only 5% of the gas’ energy comes from H₂, limiting its GHG benefit.     

Life cycle inventory study on magnesium alloy substitution in vehicles

Magnesium (Mg) alloys are suitable materials for weight reduction in vehicles because of their low density of 1.7 g/cm³ and high specific strength. The effect of Mg substitution for conventional steel parts in a vehicle on total energy consumption and CO₂ emissions was evaluated through life cycle inventory calculation. The Mg substitution reduces the total energy consumption by weight reduction, although the production energy of a Mg-substituted vehicle is higher than those of conventional and Al-substituted vehicles. The Mg substitution can save more life cycle energy consumption than the Al substitution. Recycling of Mg parts is indispensable for efficient CO₂ reduction, because the CO₂ emissions during new ingot production of Mg are much higher than those of conventional steel and Al. Strengthening of the Mg parts also can reduce the total energy consumption and CO₂ emissions. If the main body and hood are made of Mg alloy and the ratio of recycled ingot is sufficiently high, the life cycle energy consumption and CO₂ emissions will be markedly reduced.     

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.     

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 assessment of hydrogen supply chain with special attention on hydrogen refuelling stations

The controversial and highly emotional discussion about biofuels in recent years has shown that greenhouse gas² (GHG) emissions can only be evaluated in an acceptable way by carrying out a full life cycle assessment (LCA) taking the overall life cycle including all necessary pre-chains into consideration. Against this background, the goal of this paper is it to analyse the overall life cycle of a hydrogen production and provision. A state of the art hydrogen refuelling station in Hamburg/Germany opened in February 2012 is therefore taken into consideration. Here at least 50% hydrogen from renewable sources of energy is produced on-site by water electrolysis based on surplus electricity from wind (mainly offshore wind parks) and water. The remaining other 50% of hydrogen to be sold by this station mainly to hydrogen-fuelled buses is provided by trucks from a large-scale production plant where hydrogen is produced from methane or glycerol as a by-product of the biodiesel production. These two pathways are compared within the following explanations with hydrogen production from biomass and from coal. The results show that – with the goal of reducing GHG emissions on a life cycle perspective – hydrogen production based on a water electrolysis fed by electricity from the German electricity mix should be avoided. Steam methane reforming is more promising in terms of GHG reduction but it is still based on a finite fossil fuel. For a climatic sound provision of hydrogen as a fuel electricity from renewable sources of energy like wind or biomass should be used.     

Good or bad bioethanol from a greenhouse gas perspective – What determines this?

The purpose of this study is to describe how the greenhouse gas (GHG) benefits of ethanol from agricultural crops depend on local conditions and calculation methods. The focus is mainly on the fuels used in the ethanol process and biogenic GHG from the soils cultivated. To ensure that “good” ethanol is produced, with reference to GHG benefits, the following demands must be met: (i) ethanol plants should use biomass and not fossil fuels, (ii) cultivation of annual feedstock crops should be avoided on land rich in carbon (above and below ground), such as peat soils used as permanent grassland, etc., (iii) by-products should be utilised efficiently in order to maximise their energy and GHG benefits and (iv) nitrous oxide emissions should be kept to a minimum by means of efficient fertilisation strategies, and the commercial nitrogen fertiliser utilised should be produced in plants which have nitrous oxide gas cleaning. Several of the current ethanol production systems worldwide fullfill the majority of these demands, whereas some production systems do not. Thus, the findings in this paper helps identifying current “good” systems, how today’s “fairly good” systems could be improved, and which inherent “bad” systems that we should avoid.     

A comparative life cycle assessment of bio‐ and conventional fuels in a Canadian province

In this paper, a comprehensive study on corn‐based ethanol in a Canadian context is conducted, which uses the most reliable and up to date data, considers realistic assumptions, and applies sound methodology to provide a basis for developing future scenarios for corn‐based ethanol and compared the results with the conventional fuel, such as gasoline. It is estimated that the net energy value (NEV), defined as the energy content of a liter of ethanol minus the total energy use to produce a liter of ethanol, is 9.6 MJ L^?1 (LHV), when co‐products energy credits are not considered. In addition, a comparison of life cycle energy use for corn‐based ethanol and gasoline reveals that the life cycle energy use to produce a liter of ethanol is considerably less than the life cycle energy use to produce a liter of gasoline. Furthermore, a comparison of life cycle greenhouse gas (GHG) emissions for corn‐based ethanol and gasoline reveals that the life cycle GHG emissions released per liter of ethanol produced is an order of magnitude lesser than the life cycle GHG emissions released per liter of gasoline produced, when GHG emissions displaced by ethanol co‐products are considered in the estimation. Finally, a comparison of our results in terms of net fossil fuel input, net fossil fuel ratio and GHG emissions is carried out with the results obtained from the ERG biofuel analysis meta‐model (EBAMM) to reflect both Canadian and US perspectives. Copyright © 2010 John Wiley & Sons, Ltd.     

Biodiesel from microalgae – Life cycle assessment and recommendations for potential improvements

Microalgae are considered as one of the potential major source of biofuel for the future. However, their environmental benefit is still unclear and many scientific publications provide contradictory results. Here we perform the Life Cycle Assessment of the production and combustion of 1 MJ of algal methylester. The system under consideration uses standard open raceways under greenhouses. Lipid extraction and transesterification are carried out on a humid paste produced by centrifugation. Our environmental and energetic analysis shows that improving the energy balance is clearly the key priority to make microalgal cultivation sustainable and to reduce its greenhouse gas (GHG) emissions. To achieve significant reduction of the GHG emissions, most of the studies of the literature focus on technological breakthroughs, especially at the production step. However, since a large fraction of environmental impacts and especially GHG emissions do not occur directly at the production facility but stem from the production of the electricity required for producing, harvesting and transforming algae, it seems relevant to question the source of electricity as well as algae production technology. We consider a scenario where up to 45% of electricity was produced by a local renewable source and then we compare it to the improvements resulting from technological breakthroughs resulting in higher microalgal productivity or biomass concentration. It turns out that increasing the yield only drastically reduces the climate change for low starting productivity. The climate change is always significantly reduced by the use of local renewable electricity. It is therefore wiser to increase biomass productivity to easily achievable values (10–15 gm⁻² d⁻¹), and then radically change improvements pathways by considering the composition of the electricity mix used for example. At least, it must be underlined that the introduction of renewable electricity also affect energetic efficiency, leading to a positive cumulative energy balance due to better energetic ratios.     

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.     

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.