Читать книгу Handbook of Biomass Valorization for Industrial Applications - Группа авторов - Страница 63

The world’s major bioethanol renewable source is lignocellulosic biomass, therefore, it is a promising material in terms of sustainable biofuels. It is synthesized from sunlight, nutrients and carbon dioxide through capture by plants. The raw materials of lignocellulosic biomass mainly include woody substrate, agricultural residues, marine algae and municipal solid waste. These feedstock materials are renewable and can be used to produce biofuels. It was estimated that lignocellulosic biomass could produce about 80–90 billion gallons of biofuel, which could replace the huge burden of world’s fuel consumption [54, 55]. Additionally, it also offers various advantages compared to fossil fuels regarding its production, usage and products. Therefore, lignocellulosic biomass is considered sustainable in terms of its environmental safety, resource renewability and low cost in a long run. It has higher oxygen content of 10–45% compared to fossil fuels which makes it more sustainable in terms of lesser CO₂ emissions [56]. Its production doesn’t involve any infrastructural changes compared to traditional fuels and with the help of thermochemical methods and biological methods, it can be easily converted into liquid and gaseous biofuels, therefore, it is cost effective and eco-friendly.

Biofuels have some advantages and disadvantages in terms of environmental, economic and social sustainability. It has advantages in terms of carbon emission reduction, greenhouse gas reduction, energy safety, and rural development. However, it has some disadvantages related to increasing food price values, risk of increase in greenhouse gas emission by land use change for production of biofuels feedstocks, degradation of forests, land, water resources and ecosystem. The first generation biofuels obtained from feedstocks such as corn will compete with food production due to which agricultural land will be diverted into fuel production land. It will also produce risks of increase in deforestation and use of fertilizers and pesticides will cause negative effects on environments. While in second generation biofuels, economic viability is another concern. In third generation biofuels, the production of microalgae is energy intensive [57]. Therefore, to encourage sustainability of biofuels, regulatory policies like the Renewable Energy Directive (RED) have to specify various sustainability criteria for biofuels. The RED already have stipulated in 2015 that biofuels should have to reduce the greenhouse gas emissions to 50% compared to their fossil fuels, which have been raised in 2021 and now biofuels should have to lower the emissions to 65% according to the European Commission, 2018 [58]. The impact of climate change in terms of greenhouse gas emissions should be evaluated on a life cycle assessment (LCA). During production of biofuel processes, various co-products like animal feed, electricity, heat and biochemicals are produced and impact of biofuels and its co-products should be allocated. In LCA cycle of biofuels, system expansion and allocation of energy approaches are used.

Furthermore, land-use change directly transforms uncultivated land (grassland, forests) into croplands for biofuel production. Additionally, land use change indirectly induces displacement of food and feed crop production to new land areas which previously were not used for cultivation. The LCA studies accounts land use change in only 25% of their studies and include other environmental impacts by acidification, eutrophication, photochemical smog, human or eco-toxicity [57]. These environmental impacts are discussed in the following section.