A great fraction of worldwide energy carriers and material products come from fossil fuel refinery. Because of the on-going price increase of fossil resources, their uncertain availability, and their ...environmental concerns, the feasibility of oil exploitation is predicted to decrease in the near future. Therefore, alternative solutions able to mitigate climate change and reduce the consumption of fossil fuels should be promoted. The replacement of oil with biomass as raw material for fuel and chemical production is an interesting option and is the driving force for the development of biorefinery complexes. In biorefinery, almost all the types of biomass feedstocks can be converted to different classes of biofuels and biochemicals through jointly applied conversion technologies. This paper provides a description of the emerging biorefinery concept, in comparison with the current oil refinery. The focus is on the state of the art in biofuel and biochemical production, as well as discussion of the most important biomass feedstocks, conversion technologies and final products. Through the integration of green chemistry into biorefineries, and the use of low environmental impact technologies, future sustainable production chains of biofuels and high value chemicals from biomass can be established. The aim of this bio-industry is to be competitive in the market and lead to the progressive replacement of oil refinery products.
Agroforestry is a land management practice where trees are grown around or among crops or pastureland. This integration of agriculture and forestry is frequently seen as an option that can secure ...food security and co-deliver a range of environmental benefits. However, quantitative studies simultaneously integrating multiple aspects of agroforestry are rare. Focusing on four sustainability goals, namely adaptation to climate change, biodiversity conservation, climate change mitigation and rural development, this study investigated co-benefits and adverse side-effects of shaded agroforests above cocoa, coffee, oil palm, banana and citrus plantations in tropical humid West Africa. Time series of remote sensing land cover datasets were used to quantify and map recent land cover transitions in the region, and a field study in 25 agroforestry plots in Togo provided biomass carbon measurements in over 3000 trees, in addition to local farmers interviews. Estimates of theoretical agroforestry expansion and associated carbon sequestration potential in the region were compared to regional emissions from fossil fuels and deforestation. We found that about 1.6 Mha of losses in evergreen forests occurred between 1992 and 2015 (corresponding to 17% of the forest area originally present in 1992), while agricultural areas increased by 2.4 Mha (+5% relative to 1992). On average, trees in the studied agroforestry plots store 83.7 ± 7.0 t C/ha. We found synergies between rural development and adaptation benefits, no clear relationship between biodiversity and carbon storage, and a trade-off between high carbon stocks and crop yields. This trade-off can be minimized with an optimal management of agroforestry by using a mix of tree species that store medium carbon stocks and can enhance yields, soil fertility and climate resilience. In general, plant functional diversity, i.e. a balanced mix of shade trees, fruit trees, palms and bananas, emerged as a key feature of successful agroforestry systems. Besides, agroforestry trees co-products are reported as an additional, diversified source of income for local farmers. A large-scale deployment of agroforestry over seven countries in West Africa can sequester up to 135 Mt CO2/year over two decades, corresponding to about 166% of the carbon emissions from fossil fuels and deforestation in the region. Overall, agroforestry practices in tropical humid West Africa offer multiple-win solutions that are relevant to address major local and global environmental challenges. Increasing cooperation among local farmer communities, national authorities, and international organizations are instrumental to overcome the barriers for a future expansion of agroforestry systems in the region.
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This paper focuses on a Life Cycle Assessment (LCA) of four waste management strategies: landfill without biogas utilization; landfill with biogas combustion to generate electricity; sorting plant ...which splits the inorganic waste fraction (used to produce electricity via Refuse Derived Fuels, RDF) from the organic waste fraction (used to produce biogas via anaerobic digestion); direct incineration of waste. These scenarios are applied to the waste amount and composition of the Municipality of Roma (Italy) and are evaluated under different points of view: global and local emissions, total material demands, total energy requirements and ecological footprints. Results, reliable for most of the European big cities, show landfill systems as the worst waste management options and significant environmental savings at global scale are achieved from undertaking energy recycling. Furthermore, waste treatments finalized to energy recovery provide an energy output that, in the best case, is able to meet the 15% of Roma electricity consumption.
Biochar is one of the most affordable negative emission technologies (NET) at hand for future large-scale deployment of carbon dioxide removal (CDR), which is typically found essential to stabilizing ...global temperature rise at relatively low levels. Biochar has also attracted attention as a soil amendment capable of improving yield and soil quality and of reducing soil greenhouse gas (GHG) emissions. In this work, we review the literature on biochar production potential and its effects on climate, food security, ecosystems, and toxicity. We identify three key factors that are largely affecting the environmental performance of biochar application to agricultural soils: (1) production condition during pyrolysis, (2) soil conditions and background climate, and (3) field management of biochar. Biochar production using only forest or crop residues can achieve up to 10% of the required CDR for 1.5 ° C pathways and about 25% for 2 ° C pathways; the consideration of dedicated crops as biochar feedstocks increases the CDR potential up to 15–35% and 35–50%, respectively. A quantitative review of life-cycle assessment (LCA) studies of biochar systems shows that the total climate change assessment of biochar ranges between a net emission of 0.04 tCO 2 eq and a net reduction of 1.67 tCO 2 eq per tonnes feedstock. The wide range of values is due to different assumptions in the LCA studies, such as type of feedstock, biochar stability in soils, soil emissions, substitution effects, and methodological issues. Potential trade-offs between climate mitigation and other environmental impact categories include particulate matter, acidification, and eutrophication and mostly depend on the background energy system considered and on whether residues or dedicated feedstocks are used for biochar production. Overall, our review finds that biochar in soils presents relatively low risks in terms of negative environmental impacts and can improve soil quality and that decisions regarding feedstock mix and pyrolysis conditions can be optimized to maximize climate benefits and to reduce trade-offs under different soil conditions. However, more knowledge on the fate of biochar in freshwater systems and as black carbon emissions is required, as they represent potential negative consequences for climate and toxicity. Biochar systems also interact with the climate through many complex mechanisms (i.e., surface albedo, black carbon emissions from soils, etc.) or with water bodies through leaching of nutrients. These effects are complex and the lack of simplified metrics and approaches prevents their routine inclusion in environmental assessment studies. Specific emission factors produced from more sophisticated climate and ecosystem models are instrumental to increasing the resolution and accuracy of environmental sustainability analysis of biochar systems and can ultimately improve the characterization of the heterogeneities of varying local conditions and combinations of type feedstock, conversion process, soil conditions, and application practice.
Background, aim, and scope
The availability of fossil resources is predicted to decrease in the near future: they are a non-renewable source, they cause environmental concerns, and they are subjected ...to price instability. Utilization of biomass as raw material in a biorefinery is a promising alternative to fossil resources for production of energy carriers and chemicals, as well as for mitigating climate change and enhancing energy security. This paper focuses on a biorefinery concept which produces bioethanol, bioenergy, and biochemicals from switchgrass, a lignocellulosic crop. Results are compared with a fossil reference system producing the same products/services from fossil sources.
Materials and methods
The biorefinery system is investigated using a Life Cycle Assessment approach, which takes into account all the input and output flows occurring along the production chain. This paper elaborates on methodological key issues like land use change effects and soil N
2
O emissions, whose influence on final outcomes is weighted in a sensitivity analysis. Since climate change mitigation and energy security are the two most important driving forces for biorefinery development, the assessment has a focus on greenhouse gas (GHG) emissions and cumulative primary energy demand (distinguished into fossil and renewable), but other environmental impact categories (e.g., abiotic depletion, eutrophication, etc.) are assessed as well.
Results
The use of switchgrass in a biorefinery offsets GHG emissions and reduces fossil energy demand: GHG emissions are decreased by 79% and about 80% of non-renewable energy is saved. Soil C sequestration is responsible for a large GHG benefit (65 kt CO
2
-eq/a, for the first 20 years), while switchgrass production is the most important contributor to total GHG emissions of the system. If compared with the fossil reference system, the biorefinery system releases more N
2
O emissions, while both CO
2
and CH
4
emissions are reduced. The investigation of the other impact categories revealed that the biorefinery has higher impacts in two categories: acidification and eutrophication.
Discussion
Results are mainly affected by raw material (i.e., switchgrass) production and land use change effects. Steps which mainly influence the production of switchgrass are soil N
2
O emissions, manufacture of fertilizers (especially those nitrogen-based), processing (i.e., pelletizing and drying), and transport. Even if the biorefinery chain has higher primary energy demand than the fossil reference system, it is mainly based on renewable energy (i.e., the energy content of the feedstock): the provision of biomass with sustainable practices is then a crucial point to ensure a renewable energy supply to biorefineries.
Conclusions
This biorefinery system is an effective option for mitigating climate change, reducing dependence on imported fossil fuels, and enhancing cleaner production chains based on local and renewable resources. However, this assessment evidences that determination of the real GHG and energy balance (and all other environmental impacts in general) is complex, and a certain degree of uncertainty is always present in final results. Ranges in final results can be even more widened by applying different combinations of biomass feedstocks, conversion routes, fuels, end-use applications, and methodological assumptions.
Recommendations and perspectives
This study demonstrated that the perennial grass switchgrass enhances carbon sequestration in soils if established on set-aside land, thus, considerably increasing the GHG savings of the system for the first 20 years after crop establishment. Given constraints in land resources and competition with food, feed, and fiber production, high biomass yields are extremely important in achieving high GHG emission savings, although use of chemical fertilizers to enhance plant growth can reduce the savings. Some strategies, aiming at simultaneously maintaining crop yield and reduce N fertilization application through alternative management, can be adopted. However, even if a reduction in GHG emissions is achieved, it should not be disregarded that additional environmental impacts (like acidification and eutrophication) may be caused. This aspect cannot be ignored by policy makers, even if they have climate change mitigation objectives as main goal.
By altering fluxes of heat, momentum, and moisture exchanges between the land surface and atmosphere, forestry and other land‐use activities affect climate. Although long recognized scientifically as ...being important, these so‐called biogeophysical forcings are rarely included in climate policies for forestry and other land management projects due to the many challenges associated with their quantification. Here, we review the scientific literature in the fields of atmospheric science and terrestrial ecology in light of three main objectives: (i) to elucidate the challenges associated with quantifying biogeophysical climate forcings connected to land use and land management, with a focus on the forestry sector; (ii) to identify and describe scientific approaches and/or metrics facilitating the quantification and interpretation of direct biogeophysical climate forcings; and (iii) to identify and recommend research priorities that can help overcome the challenges of their attribution to specific land‐use activities, bridging the knowledge gap between the climate modeling, forest ecology, and resource management communities. We find that ignoring surface biogeophysics may mislead climate mitigation policies, yet existing metrics are unlikely to be sufficient. Successful metrics ought to (i) include both radiative and nonradiative climate forcings; (ii) reconcile disparities between biogeophysical and biogeochemical forcings, and (iii) acknowledge trade‐offs between global and local climate benefits. We call for more coordinated research among terrestrial ecologists, resource managers, and coupled climate modelers to harmonize datasets, refine analytical techniques, and corroborate and validate metrics that are more amenable to analyses at the scale of an individual site or region.
•Ecosystem services (ESs) underpin the achievement of sustainable development goals (SDGs).•Man-made ecosystem degradation may trigger pandemics.•COVID-19 interferes the flow and demand of ...ESs.•Promote the SDGs through ESs in the post-pandemic era.
The COVID-19 pandemic has stalled and rolled back progress on Sustainable Development Goals (SDGs). Ecosystem services (ESs), defined as the contributions of ecosystems to human well-being, underpin the achievement of SDGs. To promote SDG achievement in post-pandemic era, we teased out the links between ESs and SDGs while examining the impact of COVID-19. We found that ESs benefited all SDGs, yet man-made pressures led to degradation of ecosystems and their services. There is broad consensus that the virus lurks in degraded ecosystems and generates spillover due to human interference. The pandemic and global lockdown/restriction disrupted the flow of ESs and altered human ESs demand, threatening the efforts for the SDGs. We suggested: 1) to study the association and traceability of ESs-SDGs under the pandemic; 2) to prioritize pressing issues such as health care, livelihood, and resource security and in the long run, we should promote human-nature harmony to achieve the SDGs; and 3) to enhance ESs and to promote the SDGs through local community efforts, ESs accounting, and ecosystem restoration. This paper provides insights into the importance of ESs to the SDGs and the ways to integrate ESs into socio-economic development to promote the SDG achievement after the pandemic.
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Around 70 Mha of land cover changes (LCCs) occurred in Europe from 1992 to 2015. Despite LCCs being an important driver of regional climate variations, their temperature effects at a continental ...scale have not yet been assessed. Here, we integrate maps of historical LCCs with a regional climate model to investigate air temperature and humidity effects. We find an average temperature change of -0.12 ± 0.20 °C, with widespread cooling (up to -1.0 °C) in western and central Europe in summer and spring. At continental scale, the mean cooling is mainly correlated with agriculture abandonment (cropland-to-forest transitions), but a new approach based on ridge-regression decomposing the temperature change to the individual land transitions shows opposite responses to cropland losses and gains between western and eastern Europe. Effects of historical LCCs on European climate are non-negligible and region-specific, and ignoring land-climate biophysical interactions may lead to sub-optimal climate change mitigation and adaptation strategies.
Bioenergy deployment offers significant potential for climate change mitigation, but also carries considerable risks. In this review, we bring together perspectives of various communities involved in ...the research and regulation of bioenergy deployment in the context of climate change mitigation: Land‐use and energy experts, land‐use and integrated assessment modelers, human geographers, ecosystem researchers, climate scientists and two different strands of life‐cycle assessment experts. We summarize technological options, outline the state‐of‐the‐art knowledge on various climate effects, provide an update on estimates of technical resource potential and comprehensively identify sustainability effects. Cellulosic feedstocks, increased end‐use efficiency, improved land carbon‐stock management and residue use, and, when fully developed, BECCS appear as the most promising options, depending on development costs, implementation, learning, and risk management. Combined heat and power, efficient biomass cookstoves and small‐scale power generation for rural areas can help to promote energy access and sustainable development, along with reduced emissions. We estimate the sustainable technical potential as up to 100 EJ: high agreement; 100–300 EJ: medium agreement; above 300 EJ: low agreement. Stabilization scenarios indicate that bioenergy may supply from 10 to 245 EJ yr−1 to global primary energy supply by 2050. Models indicate that, if technological and governance preconditions are met, large‐scale deployment (>200 EJ), together with BECCS, could help to keep global warming below 2° degrees of preindustrial levels; but such high deployment of land‐intensive bioenergy feedstocks could also lead to detrimental climate effects, negatively impact ecosystems, biodiversity and livelihoods. The integration of bioenergy systems into agriculture and forest landscapes can improve land and water use efficiency and help address concerns about environmental impacts. We conclude that the high variability in pathways, uncertainties in technological development and ambiguity in political decision render forecasts on deployment levels and climate effects very difficult. However, uncertainty about projections should not preclude pursuing beneficial bioenergy options.
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