Werkneh Adhena Ayaliew
Department of Environmental Health, School of Public Health, College of Health Sciences, Mekelle University, P.O. Box 1871, Mekelle, Ethiopia.
Heliyon. 2022 Oct 6;8(10):e10929. doi: 10.1016/j.heliyon.2022.e10929. eCollection 2022 Oct.
Biogas is a promising bioenergy alternative to be recovered from waste/wastewater in the context of environmental sustainability and circular economy. However, raw biogas contains various secondary impurities such as carbon dioxide, hydrogen sulphide, siloxanes, nitrogen oxides (NOx), ammonia, and halogens. Depending on the emission rate of these biogas impurities, the importance of biogas is being hampered for its environmental, health and the detrimental effects possess by the impurities towards the downstream of the biogas users. Biogas impurities can cause different public health concerns (like pulmonary paralysis, asthma, respiratory diseases and deaths) and environmental impacts (such as global warming, climate change and their indirect impacts like drought, flooding, malnutrition and other disasters). The absence/inconsistent emission standards among countries, agencies, and other stakeholders is the other challenge that they possess during monitoring and controlling of these impurities. Different commercially available and emerging technologies are available for separating carbon dioxide (via biogas upgrading) and removing other biogas impurities. Technologies such as pressure swing adsorption, membrane separation, absorption-based techniques (water, chemical and physical organic solvents), cryogenic separation, and other emerging biotechnological platforms (like photobioreactor and biocatalysis) have been adopted in removing the impurities. This paper reviewed the main commercially available and new technologies and their performance in removing carbon dioxide (the main constituent of biogas) and other biogas impurities. Besides, the environmental and public health implications of biogas and future research perspectives are also highlighted.
在环境可持续性和循环经济背景下，沼气是一种有望从废物/废水中回收的生物能源替代品。然而，未经处理的沼气含有各种二次杂质，如二氧化碳、硫化氢、硅氧烷、氮氧化物（NOx）、氨和卤素。根据这些沼气杂质的排放率，沼气在环境、健康方面的重要性以及杂质对沼气用户下游造成的有害影响正受到阻碍。沼气杂质会引发不同的公共卫生问题（如肺麻痹、哮喘、呼吸系统疾病和死亡）以及环境影响（如全球变暖、气候变化及其间接影响，如干旱、洪水、营养不良和其他灾害）。各国、各机构及其他利益相关者之间缺乏/不一致的排放标准是他们在监测和控制这些杂质过程中面临的另一项挑战。有多种市售和新兴技术可用于分离二氧化碳（通过沼气提纯）及去除其他沼气杂质。已采用变压吸附、膜分离、吸收法技术（水、化学和物理有机溶剂）、低温分离以及其他新兴生物技术平台（如光生物反应器和生物催化）等技术来去除杂质。本文综述了主要的市售技术和新技术及其在去除二氧化碳（沼气的主要成分）和其他沼气杂质方面的性能。此外，还强调了沼气对环境和公共卫生的影响以及未来的研究方向。
