I. (2015), Review of methodological choices in LCA of biorefinery systems -key issues and recommendations. Biofuels, Bioprod. Bioref., 9: 606-619., which has been published in final form at http://onlinelibrary. ABSTRACTThe current trend in biomass conversion technologies is towards more efficient utilization of biomass feedstock in multi-product biorefineries. Many life cycle assessment (LCA) studies of biorefinery systems have been performed, but differ in how they use the LCA methodology. Based on a review of existing LCA standards and guidelines, this paper provides recommendations on how to handle key methodological issues when performing LCA studies of biorefinery systems. Six key issues were identified: (1) goal definition, (2) functional unit, (3) allocation of biorefinery outputs, (4) allocation of biomass feedstock, (5) land use, and (6) biogenic carbon and timing of emissions. Many of the standards and guidelines reviewed here provide only general methodological recommendations. Some make more specific methodological recommendations, but these often differ between standards. In this paper we present some clarifications (e.g. examples of research questions and suitable functional units) and methodological recommendations (e.g. on allocation).

The issue of indirect land use changes (ILUC) caused by the promotion of transport biofuels has attracted considerable attention in recent years. In this paper, we reviewed the current literature on modelling work to estimate emissions of greenhouse gases (GHG) caused by ILUC of biofuels. We also reviewed the development of ILUC policies in the EU. Our review of past modelling work revealed that most studies employ economic equilibrium modelling and focus on ethanol fuels, especially with maize as feedstock. It also revealed major variation in the results from the models, especially for biodiesel fuels. However, there has been some convergence of results over time, particularly for ethanol from maize, wheat and sugar cane. Our review of EU policy developments showed that the introduction of fuel-specific ILUC factors has been officially suggested by policymakers to deal with the ILUC of biofuels. The values proposed as ILUC factors in the policymaking process in the case of ethanol fuels are generally in line with the results of the latest modelling exercises, in particular for first-generation ethanol fuels from maize and sugar cane, while those for biodiesel fuels are somewhat higher. If the proposed values were introduced into EU policy, no (first-generation) biodiesel fuel would be able to comply with the EU GHG saving requirements. We identified a conflict between the demand from EU policymakers for exact, highly specific values and the capacity of the current models to supply results with that level of precision. We concluded that alternative policy approaches to ILUC factors should be further explored.

The area of dedicated energy crops is expected to increase in Sweden. This will result in direct land use changes, which may affect the carbon stocks in soil and biomass, as well as yield levels and the use of inputs. Carbon dioxide (CO 2 ) fluxes of biomass are often not considered when calculating the climate impact in life cycle assessments (LCA) assuming that the CO 2 released at combustion has recently been captured by the biomass in question. With the extended time lag between capture and release of CO 2 inherent in many perennial bioenergy systems, the relation between carbon neutrality and climate neutrality may be questioned. In this paper, previously published methodologies and models are combined in a methodological framework that can assist LCA practitioners in interpreting the time-dependent climate impact of a bioenergy system. The treatment of carbon differs from conventional LCA practice in that no distinction is made between fossil and biogenic carbon. A time-dependent indicator is used to enable a representation of the climate impact that is not dependent on the choice of a specific characterization time horizon or time of evaluation and that does not use characterization factors, such as global warming potential and global temperature potential. The indicator used to aid in the interpretation phase of this paper is global mean surface temperature change (DT s (n)). A theoretical system producing willow for district heating was used to study land use change effects depending on previous land use and variations in the standing biomass carbon stocks. When replacing annual crops with willow this system presented a cooling contribution to DT s (n). However, the first years after establishing the willow plantation it presented a warming contribution to DT s (n). This behavior was due mainly to soil organic carbon (SOC) variation. A rapid initial increase in standing biomass counteracted the initial SOC loss.

Ammonium nitrate and calcium ammonium nitrate are the most commonly used straight nitrogen fertilisers in Europe, accounting for 43% of the total nitrogen used for fertilisers. They are both produced in a similar way; carbonate can be added as a last step to produce calcium ammonium nitrate. The environmental impact, fossil energy input and land use from using gasified biomass (cereal straw and short rotation willow (Salix) coppice) as feedstock in ammonium nitrate production were studied in a cradleto-gate evaluation using life cycle assessment methodology. The global warming potential in the biomass systems was only 22-30% of the impact from conventional production using natural gas. The eutrophication potential was higher for the biomass systems due to nutrient leaching during cultivation, while the acidification was about the same in all systems. The primary fossil energy use was calculated to be 1.45 and 1.37 MJ per kg nitrogen for Salix and straw respectively, compared to 35.14 MJ for natural gas. The biomass production was assumed to be self-supporting with nutrients by returning part of the ammonium nitrate produced together with the ash from the gasification. For the production of nitrogen from Salix, it was calculated that 3914 kg of nitrogen can be produced every year from 1 ha, after that 1.6% of the produced nitrogen has been returned to the Salix production. From wheat straw, 1615 kg of nitrogen can be produced annually from 1 ha, after that 0.6% of the nitrogen has been returned.

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The production of nitrogen fertilizers are almost exclusively based on fossil feedstocks such as natural gas and coal. Nitrogen fertilizers are a necessity to maintain the high agricultural production that the world's population currently demands. Ammonia produced from nonfossil-based feedstocks would enable renewable production of ammonia. Renewable feedstocks are one thing, but perhaps even more important in the future are the security of supply that decentralized production enables. In this study, the technoeconomic evaluation of production of ammonia from various renewable feedstocks and for several plant sizes was investigated. The feedstocks included in this study are gridbased electricity produced from wind power, biogas, and woody biomass. The feedstocks differed in exergy, and to make a fair comparison, the electric equivalence ratios method was used. The results showed that the energy consumption for biogas and electricity is the same at 42 GJ/ tonne ammonia. When using the electric equivalence comparison for the same cases, the results are 26 and 42 GJ/ tonne, respectively. Biomass-based production has an energy consumption of 58 GJ/tonne and 31 GJ/tonne when using the electric equivalence comparison, which should be compared with the industrial average of 37 GJ (or 21 GJ electric equivalence) per tonne of ammonia. Monte Carlo simulations were used to vary the inputs to the process to evaluate the production cost. The ammonia production cost ranged from $680 to 2300/tonne ammonia for the various cases studied.

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BackgroundBiodiesel is the main liquid biofuel in the EU and is currently mainly produced from vegetable oils. Alternative feedstocks are lignocellulosic materials, which provide several benefits compared with many existing feedstocks. This study examined a technical process and its mass and energy balances to gain a systems perspective of combined biodiesel (FAME) and biogas production from straw using oleaginous yeasts. Important process parameters with a determining impact on overall mass and energy balances were identified and evaluated.ResultsIn the base case, 41% of energy in the biomass was converted to energy products, primary fossil fuel use was 0.37 MJprim/MJ produced and 5.74 MJ fossil fuels could be replaced per kg straw dry matter. The electricity and heat produced from burning the lignin were sufficient for process demands except in scenarios where the yeast was dried for lipid extraction. Using the residual yeast cell mass for biogas production greatly increased the energy yield, with biogas contributing 38% of total energy products.ConclusionsIn extraction methods without drying the yeast, increasing lipid yield and decreasing the residence time for lipid accumulation are important for the energy and mass balance. Changing the lipid extraction method from wet to dry makes the greatest change to the mass and energy balance. Bioreactor agitation and aeration for lipid accumulation and yeast propagation is energy demanding. Changes in sugar concentration in the hydrolysate and residence times for lipid accumulation greatly affect electricity demand, but have relatively small impacts on fossil energy use (NER) and energy yield (EE). The impact would probably be greater if externally produced electricity were used.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0640-9) contains supplementary material, which is available to authorized users.