Increasing Bioenergy Production Research Articles

Bioenergy in Europe is unlikely to make a timely contribution to climate change targets

Increasing bioenergy production is a significant component of European efforts to mitigate climate change, but has contested potential for reducing emissions. We use an integrated land system model to explore the effects of large-scale bioenergy production within the European Union on carbon balances. We find that increased bioenergy crop production is likely to cause substantial deforestation and a commensurate loss of associated carbon stocks largely due to displacement of food production from other areas. Deforestation would occur either within the EU if European forests were not protected, or in other parts of the world arising from indirect land use change if European forests were protected. The net carbon benefit of bioenergy production is largely negative, or uncertain, even under the most optimistic levels of fossil fuel replacement, and will not offset initial carbon losses over the coming 50 yr. The growth of intensive agriculture required to satisfy the demand for bioenergy and food will have negative impacts on crucial ecosystem services. Overall, we identify substantial disadvantages to increasing bioenergy production relative to freeing land for natural succession. At best, large-scale bioenergy production is likely to be irrelevant to time-sensitive climate targets.

Harvested winter rye energy cover crop: multiple benefits for North Central US

Cover crops (CCs) can reduce nitrogen (N) loss to subsurface drainage and can be reimagined as bioenergy crops for renewable natural gas production and carbon (C) benefits (fossil fuel substitution and C storage). Little information is available on the large-scale adoption of winter rye for these purposes. To investigate the impacts in the North Central US, we used the Root Zone Water Quality Model to simulate corn-soybean rotations with and without winter rye across 40 sites. The simulations were interpolated across a five-state area (IA, IL, IN, MN, and OH) with counties in the Mississippi River basin, which consists of ∼8 million ha with potential for rye CCs on artificially drained corn-soybean fields (more than 63 million ha total). Harvesting fertilized rye CCs before soybean planting in this area can reduce N loads to the Gulf of Mexico by 27% relative to no CCs, and provide 18 million Mg yr−1 of biomass-equivalent to 0.21 EJ yr−1 of biogas energy content or 3.5 times the 2022 US cellulosic biofuel production. Capturing the CO2 in biogas from digesting rye in the region and sequestering it in underground geologic reservoirs could mitigate 7.5 million Mg CO2 yr−1. Nine clusters of counties (hotspots) were identified as an example of implementing rye as an energy CC on an industrial scale where 400 Gg yr−1 of rye could be sourced within a 121 km radius. Hotspots consisted of roughly 20% of the region’s area and could provide ∼50% of both the N loss reduction and rye biomass. These results suggest that large-scale energy CC adoption would substantially contribute to the goals of reducing N loads to the Gulf of Mexico, increasing bioenergy production, and providing C benefits.

Impact of Bioenergy on Economic Growth and Development: An European Perspective

The development of a country's economy depends heavily on its access to energy. It is extensively used in agriculture and related industries, including the production and delivery of fertilisers, pesticides, and farm equipment. This study investigated the impact of Bioenergy on economic growth and development in Europe with major focus on Greece. The study used a questionnaire to collect data from 400 professionals in the energy sector in Greece. The study showed that increased bioenergy production positively affects economic growth and development. It was established that there is a significant relationship between dependence on renewable and low-carbon energy systems and investing in sources of bioenergy positively affect economic growth and development. Households require bioenergy for heating, lighting, and cooking. Electricity, coal, petroleum, natural gas, uranium, and other fuels can all be used to produce energy. Bioenergy influences a state's economic performance and a good correlation with the level of innovation in the industry or with energy derived from natural gas. The article discusses the disparity in bioenergy use across nations as well as how they have changed during the investigated time. All of these factors lend credence to the advantages that bioenergy will bring about for the long-term growth of the bioeconomy. Production of bioenergy has the potential to significantly reduce climate change while long-term energy resource diversification is guaranteed.

Microbial Fuel Cells for Electrical Energy: Outlook on Scaling-Up and Application Possibilities towards South African Energy Grid

Microbial fuel cell (MFC) technology turns chemical energy into bioelectricity in a clean and efficient manner, lowering carbon emissions and increasing bioenergy production. It is a multifaceted technique that has the potential to be a panacea for clean water scarcity and sustainable, renewable energy. In this review, the approach focuses on scaling-up and application prospects at a commercial scale. An outlook on various, previously tried methodologies was generated in order to establish a viable bioelectricity scaling-up approach that is also cost-effective in its design. Precise themes were followed to evaluate previously produced models and methodologies for MFCs: principle and anatomical mechanisms, basic applications, bioelectricity scaling-up potentials from previous work and limitations, then an outlook on MFC feasibility and its wastewater treatment plant (WWTP) energy supply chain. The goal of this paper is to derive a viable approach from prior research in order to comprehend how MFC technology may be scaled-up for commercial and practical power output. Essentially, this article summarizes the current energy predicaments faced by South Africa and proposes MFCs as a new knowledge-contributing technology with electricity scaling-up potential. Conclusively, more research on MFC technique scaling-up operating factors is recommended.

Will Brazil’s push for low-carbon biofuels contribute to achieving the SDGs? A systematic expert-based assessment

Bioenergy can be part of strategies towards achieving climate and energy-related UN Sustainable Development Goals, especially for land abundant countries. Biofuel advocates argue that such strategies advance at least one-third of the SDGs, whereas opponents claim that they lead to negative trade-offs. Numerous studies have explored the benefits and risks of early bioenergy policies. Here we study the new Brazilian biofuel policy Renovabio, which was designed to increase the share of biofuels in the national energy mix of the world’s second largest biofuel producer to 18%. We use an impact score scheme to assess the potential effects of the policy on the SDGs based on expert opinions and triangulate our findings with a literature review. Our results indicate that these experts entertain high expectations for the policy’s mechanisms to increase bioenergy production and promote the substitution of fossil fuels. The policy is expected to support climate-related, economic and technological SDG targets, while potential impacts in other SDG dimensions, such as environmental, social, and health targets are contradictory. Our results reflect the positions in the debate around biofuels and indicate a need for effective sustainability safeguards to ensure that national policies like Renovabio actually live up to their declared objectives.

Exploring the effects of land management change on productivity, carbon and nutrient balance: Application of an Ensemble Modelling Approach to the upper River Taw observatory, UK

Agriculture is challenged to produce healthy food and to contribute to cleaner energy whilst mitigating climate change and protecting ecosystems. To achieve this, policy-driven scenarios need to be evaluated with available data and models to explore trade-offs with robust accounting for the uncertainty in predictions. We developed a novel model ensemble using four complementary state-of-the-art agroecosystems models to explore the impacts of land management change. The ensemble was used to simulate key agricultural and environmental outputs under various scenarios for the upper River Taw observatory, UK. Scenarios assumed (i) reducing livestock production whilst simultaneously increasing the area of arable where it is feasible to cultivate (PG2A), (ii) reducing livestock production whilst simultaneously increasing bioenergy production in areas of the catchment that are amenable to growing bioenergy crops (PG2BE) and (iii) increasing both arable and bioenergy production (PG2A + BE). Our ensemble approach combined model uncertainty using the tower property of expectation and the law of total variance. Results show considerable uncertainty for predicted nutrient losses with different models partitioning the uncertainty into different pathways. Bioenergy crops were predicted to produce greatest yields from Miscanthus in lowland and from SRC-willow (cv. Endurance) in uplands. Each choice of management is associated with trade-offs; e.g. PG2A results in a significant increase of edible calories (6736 Mcal ha−1) but reduced soil C (−4.32 t C ha−1). Model ensembles in the agroecosystem context are difficult to implement due to challenges of model availability and input and output alignment. Despite these challenges, we show that ensemble modelling is a powerful approach for applications such as ours, offering benefits such as capturing structural as well as data uncertainty and allowing greater combinations of variables to be explored. Furthermore, the ensemble provides a robust means for combining uncertainty at different scales and enables us to identify weaknesses in system understanding.

Assessment of Soil Physical Quality and Water Flow Regulation under Straw Removal Management in Sugarcane Production Fields

Removing sugarcane straw to increase bioenergy production can generate significant income to the industry. However, straw contributes to the regulation of soil functions and consequently supports the provision of ecosystem services, such as water flow regulation. Thus, straw removal may hinder the provision of these services, especially in mechanized sugarcane production systems, which have soil compaction problems due to machinery traffic. In this study, we assess a six-year experiment in Brazil with four rates of straw removal: 0 Mg ha−1 (TR), 5 Mg ha−1 (HR), 10 Mg ha−1 (LR), and 15 Mg ha−1 (NR) remaining straw. Using attributes, such as soil bulk density, porosity, water infiltration, runoff, saturated hydraulic conductivity and available water-holding capacity, as indicators of key soil functions, we calculated a soil-related ecosystem service (ES) index for water flow regulation provision. The ES index revealed that water flow regulation was low regardless of the straw management (0.56, 0.63, 0.64 and 0.60 for TR, HR, LR and NR, respectively). It can be a consequence of soil compaction caused by machinery traffic throughout the successive cycle, whose straw was unable to mitigate this issue. Thus, by the end of the sugarcane cycle (sixth ratoon), straw removal had little effect on soil physical and hydraulic indicators, and consequently had little impact on the provision of the soil-related ES associated with water flow regulation. Nevertheless, straw management should be planned to consider other functions and soil-related ES benefited by straw retention.

Methods of Increasing Miscanthus Biomass Yield for Biofuel Production

The lignocellulosic perennial crop miscanthus, especially Miscanthus × giganteus, is particularly interesting for bioenergy production as it combines high biomass production with low environmental impact. However, there are several varieties that pose a hazard due to susceptibility to disease. This review contains links showing genotype and ecological variability of important characteristics related to yield and biomass composition of miscanthus that may be useful in plant breeding programs to increase bioenergy production. Some clones of Miscanthus × giganteus and Miscanthus sinensis are particularly interesting due to their high biomass production per hectare. Although the compositional requirements for industrial biomass have not been fully defined for the various bioenergy conversion processes, the lignin-rich species Miscanthus × giganteus and Miscanthus sacchariflorus seem to be more suitable for thermochemical conversion processes. At the same time, the species Miscanthus sinensis and some clones of Miscanthus × giganteus with low lignin content are of interest for the biochemical transformation process. The species Miscanthus sacchariflorus is suitable for various bioenergy conversion processes due to its low ash content, so this species is also interesting as a pioneer in breeding programs. Mature miscanthus crops harvested in winter are favored by industrial enterprises to improve efficiency and reduce processing costs. This study can be attributed to other monocotyledonous plants and perennial crops that can be used as feedstock for biofuels.

Cadmium accumulation in rice straws and derived biochars as affected by metal exposure, soil types and rice genotypes

Straw residues, as one of the conservation farming practices, are being strongly encouraged in China, including some cadmium-polluted areas. Nowadays, a portion of this plant residue is promoted to be removed for reducing excess metal(loid) in the soil and to be used for bioenergy production. Nevertheless, the possible influences of contaminated straw or the burial of its derived biochars on Cd accumulation in soil and data based on health risk assessment associated with different status and extent of soil contamination were relatively unknown. Thus it is important to provide a more systematical understanding of contaminated straw burial at specific contamination zones, which may provide useful guidance for straw utilization. In this study, we harvested two genotypes of rice straw from 6 contaminated levels among three soil types to comprehensively study the total Cd contents in straws and its derived biochars and correlate the sets of straw characteristics and Cd contents in three different contamination zones. The total Cd concentration in straws grew at a steady rate relatively with increasing soil Cd contamination levels, compared to those in biochars which performed more fluctuate due to the strong burning. According to correlational analyses, three-way ANOVA showed that the moisture, ash, volatile and fixed carbon were all significantly affected by straw CdTotal contents (p < 0.001). Such relationships were attributed to guide straw removal portions for gasification. Meanwhile, there was a significant correlation between straw Cd concentration and soil types (p < 0.001), confirming that it might be worth determining soil remediation by straw removal according to site-specific farmland conditions. This work will help to assess efforts toward predicting Cd concentration in the paddy soils related to kinds of contamination status and would also give useful guidance to make sustainable management strategies for crop straws in polluted regions. Novelty statement This work provided data on how much rice straw is needed to remove to ensure the minimal amount to control soil contamination and reduce costs according to site-specific conditions and soil Cd contamination status. It also explains the correlations between straw characteristics related to bioenergy use and soil conditions which would give guidance to balance using crop straw for increased bioenergy production and the need to also protect, preserve, and enhance soil resources.

Soil health response to sugarcane straw removal in Brazil

Sugarcane straw removal is a promising strategy to increase bioenergy production in Brazil. However, if straw removal is not properly managed, it may lead to soil health degradation, thus threatening sustainability of the entire bioenergy production system. In this context, a comprehensive assessment was conducted in 12 field experiments located in central-southern Brazil, the world’s largest sugarcane-producing region, to investigate the impacts of straw removal scenarios on soil health, using the Soil Management Assessment Framework (SMAF). Two groups of experiments were arranged in this study, consisting of three (no–NR; moderate–MR; and total removal–TR) and four straw removal treatments (NR; low–LR; high–HR; and TR). Soil samples were collected (0–10 and 10−20 cm) to evaluate a selected set of soil health indicators (i.e., pH, available phosphorus, exchangeable potassium, bulk density and soil organic carbon). Indicators were individually scored and then integrated into an overall Soil Health Index (SHI) and its chemical, physical, and biological components. Datasets were analyzed by site, experiment groups and soil texture (clayey and sandy soils) and the relationships among straw removal, soil health, and sugarcane yield were also investigated. Our findings showed that soil health responses to straw removal were properly detected by SMAF scoring curves. Based on SHI, sandy and clayey soils were functioning at 41–56% and 67–86% of their full potential, respectively. Soil health degradation was mostly induced by TR and HR, while LR and MR resulted in minimal detrimental effects on a short-term basis compared with NR. However, sandy soils were more prone to soil health degradation, indicating that straw removal should be avoided on those soils. For clayey soils, decline in soil health was driven by physical degradation. Healthier soils were associated with higher sugarcane stalk yields, and physical degradation was the main driver for crop yield losses. Conclusions drawn from this study suggest that comprehensive soil health assessments by integrating chemical, physical and biological indicators are fundamental to design more sustainable straw management and bioenergy production systems in Brazil.

Land Use and Management Effects on Sustainable Sugarcane-Derived Bioenergy

Bioenergy is an important and feasible option for mitigating global warming and climate change. However, large-scale land-use change (LUC) to expand bioenergy crops, such as sugarcane, raises concerns about the potential negative environmental and socioeconomic side effects. Such effects are context-specific, and depending on the LUC scenario and management practices, several co-benefits can be attained. We reviewed the literature and discussed how LUC and best management practices affect key components of sustainability (e.g., soil health, soil carbon (C) sequestration, greenhouse gas emissions (GHG) emissions, nutrient cycling, water quality, among others) of sugarcane-derived bioenergy production in Brazil. Sugarcane expansion has occurred predominantly over pasture areas, although converting croplands could be also an environmentally feasible option. The land transition from low-productivity pastures to sugarcane cultivation seems to be a sustainable pathway to increase bioenergy production. This LUC scenario enhances soil health and soil C sequestration over time, although soil compaction, biodiversity loss, and erosion are still challenging. Besides, adopting best management practices, such as conservation tillage, sustainable crop residue management, rational fertilization, and recycling by-products, has been fundamental to ensuring sustainable bioenergy production. Public policies and well-designed legal frameworks and regulations, such as the Forest Code and the RenovaBio legislations in Brazil, are necessary to make bioenergy production compatible with rational land use and protection. Lastly, our analysis provided insights into sugarcane expansion over a small proportion (1%) of pasture areas in Latin American and Caribbean (LAC) and sub-Saharan African (SSA) countries, which may result in a substantial impact on global bioenergy supply. We concluded that sugarcane-derived bioenergy is a sustainable option to tackle climate change while provisioning other key ecosystem services and promoting socioeconomic development.

EU28 region's water security and the effect of bioenergy industry sustainability.

Water is an essential component of agriculture-food production. As the biomass and biofuel are known excellent sources of renewable and sustainable energy, cultivating process consumes significant quantities of water. Without sufficient, good-quality and easily accessible water, the European agriculture-food production could thus be under threat. This research analyses the impact of the water supply on the bioenergy production in the 28 European Union countries, for the 1990-2018 period within the pathway of the European Union 2030 agenda for sustainable development. The findings using the generalised least squares (GLS) technique show that bioenergy production and population density appear to decrease water supply. Precisely, the magnitude of the effects is - 0.224 and - 0.136 for developing countries and developed countries in the EU, respectively. This indicates that a serious reduction of water security is more likely to happen in developed countries than in developing countries as a result of the increase in bioenergy consumption. In the meantime, fossil fuel, income generation activities and institutional quality have already positively affected water supply. Thus, these findings implied that water scarcity is becoming one of the main obstacles for bioenergy expansion and growth. The results were also further verified by the random effect and pooled oriented least squares method. This study recommends that the Member of the European Union States should continue to increase bioenergy production in the energy mix efforts without any strenuous water security issues. Notwithstanding, there are several situations where a developing bioenergy industry is unlikely to be constrained by water shortage, and with the drive of bioenergy demand, the efforts might unlock new opportunities to adapt to water-related challenges and to improve water usage efficiencies. The authorities should illustrate organised water security and sustainable bioenergy policy by way of developing alternative strategies in reducing fossil fuel power and related CO2 emissions, accordingly to the unique characteristics of both developed and developing countries in the EU.

Importance of sugarcane straw maintenance to prevent soil organic matter depletion in a Nitisol in the central-southern region of Brazil

Sugarcane straw is a potential feedstock to increase bioenergy production. However, leaving straw on the soil surface is important to sustaining soil organic matter (SOM). We conducted a field experiment to evaluate the impacts of two years of straw removal on SOM in a sugarcane area – on an Eutric Nitisol in south-eastern Brazil – with low straw production (7 Mg ha–1). The experiment was a randomised complete block design (four blocks) with four rates of straw removal: (i) no removal, (ii) medium removal, (iii) high removal and (iv) total removal. We evaluated straw decomposition, soil carbon (C) and nitrogen (N) stock (0–30 cm), labile C, and microbial biomass C and N (0–10 cm). Increases in the straw removal rates reduced decomposition, with 30–42% of the initial straw amount remaining on the soil after one year (first year) and 33–38% remaining at the end of the second year. During the first year, no effect was found on soil C (8 kg m–2) and N (0.7 kg m–2) stocks; however, during the second year, total straw removal reduced soil C stock by 10% (0–30 cm) compared with no straw removal. Straw removal rates negatively affected the labile C (6–10% and 20–25%, first and second year respectively) and microbial C (correspondingly 10–15% and 21–27%). Microbial N was not altered in the first year, but decreased 26% due to straw maintenance (no removal) during the second year. Total straw removal decreased the C management index (CMI) by 15% (first year) compared with no straw removal. However, during the second year, all rates of straw removal decreased the CMI: by 15% for medium, 22% for high and 26% for total removal. Our findings indicate that any straw removal in areas with low straw production negatively affects SOM, initially through reduction in labile C pools. Although slight impacts on soil C and N stock were detected, reduction in straw-derived inputs stimulates microbial utilisation of soil C pools, and consequently reduces SOM over time.

Value-addition of wheat straw through acid treatment and pyrolysis of acid treated residues

Agricultural straw utilization has become a big concern in many countries with abundance of the production. While different comprehensive utilization methods have been used for the bio-oil production, complete uses of the waste biomass into useful products need to be examined to reduce the environmental burdens of agricultural straw disposal. By deploying value addition of straw biomass, this article evaluates the two process for the complete utilization of straw including acid treatment into carbohydrates rich compounds and acid treated residue pyrolysis to phenolic and ketonic rich compounds. Effects of intrinsic alkaline and alkaline earth metals on wheat straw pyrolysis behavior and product distribution investigated. Acid pickling was executed employing HCl, HF and HCl + HF solution. Pyrolysis products of acid treated wheat straw were investigated. Fixed bed reaction results showed that acid pickling is beneficial to the production of liquid, the yield of liquid increased from 37.48 wt% raw wheat straw to 42.24 wt% wheat straw-HCl, 48.03 wt% wheat straw –HF, and 47.20 wt% wheat straw-HCl + HF. The relative content of compounds identified by GC/MS in bio-oil changed significantly after acid pickling. Sugar increased from 1.43% wheat straw to 25.27% wheat straw-HCl, 19.00% wheat straw-HF and 19.78% wheat straw-HCl + HF. Particularly, D-Allose, which has been increased from 0.19% wheat straw to 22.18% wheat straw-HCl), 7.22% wheat straw-HF), and 7.89% wheat straw-HCl + HF. These results provide evidence that the straw biomass has good potential to increase bioenergy production.

Enhanced bioenergy production in rural areas: Synthetic urine as a pre-treatment for dry anaerobic fermentation of wheat straw

Straw and urine have always been two major problems in rural environmental management worldwide. Realizing the recycle of resources is possible to solve the dual problems of resources and environment. In this study, synthetic urine was proposed as a pretreatment method for wheat straw. The effects and application potential of synthetic urine on anaerobic fermentation of wheat straw were explored by comparing the start-up time, pH, methane production and other parameters of dry anaerobic fermentation system with four other traditional pretreatment and non-pretreatment (control). The results showed that the synthetic urine can effectively destroy the fiber structure of straw and beneficial to control the pH in the optimal range to avoid acidogenesis, speeding up the methanogenesis process (10 d). Compared with the control group, the total solid gas production rate and volume gas production rate after pretreatment with 1: 3 dilution of synthetic urine increased by 56.3% and 100%, reaching 195.73 mL g−1 and 1.20 m3 (m3 d) −1. The startup time of the system is also shortened by 11 d. Compared with other pretreatment groups, the methanogenesis process after synthetic urine pretreatment was the shortest (39 d), and the maximum methane production reached 121.5 mL g−1 VS. These results provide evidence that the synthetic urine has good potential to co-ferment with straw to increase bioenergy production in rural areas.

Impacts of Increasing Bioenergy Production on Timber Harvest and Carbon Emissions

Using a partial equilibrium model of the Swedish forest sector, this study analyzes the impacts of an increasing bioenergy production on the timber harvest and forest growing stock. The impacts on ...

Soil Macrofauna Responses to Sugarcane Straw Removal for Bioenergy Production

Sugarcane (Saccharum officinarum) residue (straw) has been identified as a promising feedstock for bioenergy production, but excessive straw removal may impair soil macrofauna and related ecosystem services. To quantify straw removal effects on abundance, richness, and diversity of soil macrofauna, four experiments were conducted in Sao Paulo state, Brazil, under different edaphoclimatic conditions. A secondary goal was to evaluate seasonal changes on soil macrofauna and identify linkages between those changes and soil chemical and physical attributes. Four straw removal treatments (NR, no removal, LR, low removal, HR, high removal, and TR, total removal) were evaluated. Macrofauna and other soil attributes were sampled within the 0- to 0.30-m depth increment. Soil macrofauna were impaired by TR with the magnitude of response being related to both edaphoclimatic conditions and management practices. Numerous interactions among seasons, straw removal rates, and soil macrofauna were found, especially for total abundance and diversity of organisms. Partial straw removal (HR and LR) may be a strategy to protect soil health and increase bioenergy production with minimal effects on soil macrofauna, although long-term experiments are needed to confirm our hypothesis. The NR treatment generally had better soil quality as indicated by greater soil moisture, macropore number, soil organic carbon (SOC) content, and soil fertility, which led to a higher abundance of most macrofauna organisms. Total removal resulted in greater soil compaction and decreased macrofauna abundance, especially in clay soils. Our findings confirm that an integrated approach using soil indicators as guidelines should be adopted to better predict sustainable straw management practices for sugarcane in Brazil.

Pyrolysis coupled anaerobic digestion process for food waste and recalcitrant residues: Fundamentals, challenges, and considerations

AbstractFood waste (FW) is a severe environmental problem all over the world, and the recalcitrant organic residues (ROR) from FW treatment plant operations are also a critical environmental issue due to unsustainable treatment and disposal techniques. Requirements for FW and ROR complete exploitation with the establishment of recycling‐renewable technologies are very crucial. This paper review AD and pyrolysis as two promising technologies to degrade FW and its residues, creating numerous renewable bioenergy yields with value‐added. Existing oil/tar application methods in the AD suffered from various problems such as microorganism toxicity and limited productivity. Future upgrading techniques considering the second‐stage pyrolysis process to decompose oil/tars for syngas with high hydrogen content and enhanced bio‐methanation in the AD were addressed. Simultaneous pyrolysis by‐product recycle in the AD during the valorization of FW are aimed to have the features of sustainability toward increased bioenergy production, reactor efficiency, and agricultural application.

LCA of anaerobic digestion: Emission allocation for energy and digestate

Anaerobic digestion produces renewable energy and recycled fertilisers, and thereby may improve energy and nutrient self-sufficiency and decrease greenhouse gas (GHG) emissions from energy production, agriculture and waste management. Finland aims to increase bioenergy production and nutrient recycling from agricultural biomass, via digestion of non-food crops and side streams from food production. According to the national climate and energy strategy, the life cycle carbon balance of bioenergy must be accounted for to ensure its sustainability. However, all emissions and abatement potential are often allocated only for energy and not for digestate production and use. This emphasises climate impacts for energy, and fails to consider digestate-related emissions and credits. This study used different allocation methods to assess the climate emissions of the entire anaerobic digestion chain from feedstock procurement to both energy and digestate use in comparison to fossil energy and mineral fertiliser. Three feedstock scenarios with pig slurry and different co-feedstocks (separated solid fraction of slurry or grass from uncultivated fields or food industry side streams) were assessed. The climate emissions of energy were decreasing and the climate emissions of digestate were increasing when allocating all emissions from anaerobic digestion to energy and moving towards using economic allocation method and finally mass allocation method. With all allocation methods the three scenarios with different co-feedstocks led to lower climate emissions compared to the production of fossil fuels and mineral fertilisers. The climate emissions of anaerobic digestion were highest for the scenario that made use of grass as co-feedstock and lowest with food industry side streams as co-feedstock. The largest climate emissions of anaerobic digestion were from combined heat and power plant, and manure storage. When looking further the digestate storage, transportation and utilization as fertiliser on field the emissions were higher compared to mineral fertiliser utilization on field. However, when combining emissions of anaerobic digestion allocated for digestate and emissions of the digestate utilization on field, they were lower compared to mineral fertiliser production and use on field. The largest climate emissions of digestate were from digestate field use.

Thermal Properties of Residual Agroforestry Biomass of Northern Portugal

Biomass from forestry and agricultural sector provides an important contribution to encounter the government’s targets for increasing bioenergy production and utilization. Characterization of agricultural and forest wastes are critical for exploiting and utilizing them for energy purpose. In the present work agricultural and forest wastes and shrubs were sampled in two sites in north Portugal (Ave and Sabor basin) and subjected to Higher Heating Value (HHV) and chemical composition quantification. The HHV was evaluated according to the methodology described in Standard DD CEN/TS14918:2005. For the lignin content, the procedure was made by the Klason method and the extractives content was determined with the Soxhlet method. For agricultural and forest wastes the HHV values are identical with a range of 17 to 21 MJ·kg−1. However, shrubs biomass presentx slightly higher and statistically different values from agricultural and forest wastes, varying between 19 and 21 MJ·kg−1. Forest wastes contain higher levels of holocellulose compared to agricultural wastes and, with respect to extractive contents, this trend is the reverse. There is a general tendency for the woody components present thermo-chemical properties more suited for energy purposes, than the residues formed by the branches and leaves.