Sustainable Industrial Systems, School of Chemical Engineering and Analytical Science, The University of Manchester , Manchester , UK.
Dipartimento di Scienze Agrarie e Ambientali - Produzione, Territorio, Agroenergia, Università degli Studi di Milano , Milan , Italy.
Front Bioeng Biotechnol. 2016 Mar 11;4:26. doi: 10.3389/fbioe.2016.00026. eCollection 2016.
The aim of this study was to evaluate life cycle environmental impacts associated with the generation of electricity from biogas produced by the anaerobic digestion (AD) of agricultural products and waste. Five real plants in Italy were considered, using maize silage, slurry, and tomato waste as feedstocks and cogenerating electricity and heat; the latter is not utilized. The results suggest that maize silage and the operation of anaerobic digesters, including open storage of digestate, are the main contributors to the impacts of biogas electricity. The system that uses animal slurry is the best option, except for the marine and terrestrial ecotoxicity. The results also suggest that it is environmentally better to have smaller plants using slurry and waste rather than bigger installations, which require maize silage to operate efficiently. Electricity from biogas is environmentally more sustainable than grid electricity for seven out of 11 impacts considered. However, in comparison with natural gas, biogas electricity is worse for seven out of 11 impacts. It also has mostly higher impacts than other renewables, with a few exceptions, notably solar photovoltaics. Thus, for the AD systems and mesophilic operating conditions considered in this study, biogas electricity can help reduce greenhouse gas (GHG) emissions relative to a fossil-intensive electricity mix; however, some other impacts increase. If mitigation of climate change is the main aim, other renewables have a greater potential to reduce GHG emissions. If, in addition to this, other impacts are considered, then hydro, wind, and geothermal power are better alternatives to biogas electricity. However, utilization of heat would improve significantly its environmental sustainability, particularly global warming potential, summer smog, and the depletion of abiotic resources and the ozone layer. Further improvements can be achieved by banning open digestate storage to prevent methane emissions and regulating digestate spreading onto land to minimize emissions of ammonia and related environmental impacts.
本研究旨在评估由农产品和废物的厌氧消化（AD）产生的沼气发电的生命周期环境影响。考虑了意大利的五个实际工厂，使用青贮玉米、浆料和番茄废物作为饲料，并同时产生电力和热能；后者未被利用。结果表明，青贮玉米和厌氧消化器的运行，包括消化物的露天储存，是沼气发电影响的主要贡献者。使用动物浆料的系统是最佳选择，除了海洋和陆地生态毒性。结果还表明，与需要青贮玉米来高效运行的更大装置相比，使用浆料和废物的较小工厂在环境方面更具优势。沼气发电在 11 项影响中有 7 项比电网发电更具环境可持续性。然而，与天然气相比，沼气发电在 11 项影响中有 7 项更差。与其他可再生能源相比，它的大部分影响也更高，除了一些例外，特别是太阳能光伏发电。因此，对于本研究中考虑的 AD 系统和中温操作条件，沼气发电可以帮助减少温室气体（GHG）排放，相对于化石密集型电力组合；然而，其他一些影响会增加。如果减少气候变化是主要目标，那么其他可再生能源具有更大的潜力来减少 GHG 排放。如果除了这一点之外，还考虑到其他影响，那么水力、风能和地热能是沼气发电的更好替代品。然而，利用热能将显著提高其环境可持续性，特别是全球变暖潜能、夏季烟雾和非生物资源以及臭氧层的消耗。通过禁止露天储存消化物以防止甲烷排放，并规范消化物在土地上的散布以最大程度地减少氨排放和相关的环境影响，可以进一步改善。
