A Human Health Toxicity Assessment of Biogas Engines Regulated and Unregulated Emissions

Abstract

The aim of the work is to evaluate the damage to human health arising from emissions of in-operation internal combustion engines fed by biogas. The need of including also unregulated emissions like polycyclic aromatic hydrocarbons (PAHs), aldehydes and dioxins and furans is twofold: (i) to cover the lack in biogas engine emissions measurements and (ii) to complete the picture on biogas harmfulness to human health by identifying the substances with the highest impact. To this purpose, an experimental campaign is conducted on six biogas engines and one fed by natural gas all characterised by an electric power of 999 kWel. Collected data are used to perform an impact analysis on human health combining the Health Impact Assessment and the Risk Assessment. Measurements show that PAHs, aldehydes and diossin and furans are almost always below the detection limit, in both biogas and natural gas exhausts. The carcinogenic risk analysis of PAHs for the two fuels established their substantial equivalence. The analysis of equivalent toxicity of dioxins and furans reveals that biogas is, on average, 10 times more toxic than natural gas. Among regulated emissions, NOx in the biogas engines exhausts are three times higher than those of natural gas. They are the main contributors to human health damage, with approximately 90% of the total. SOx ranks second and accounts for about 6% of the total damage. Therefore, (i) the contribution to human health damage of unregulated emissions is limited compared to the damage from unregulated emissions, (ii) the damage per unit of electricity of biogas engines exhausts is about three times higher than that of natural gas and it is directly linked to NOx, (iii) obtaining a good estimation of the human health damage from both biogas and natural gas engines emissions is enough of a reason to consider NOx and SOx.

Impact of Compressed Natural Gas (CNG) Fuel Systems in Small Engine Wood Chippers on Exhaust Emissions and Fuel Consumption

“…The adaptation of IC engines to combustion of gaseous fuels may become a contemporary scientific trend as to the use of biogas [90][91][92]. Biogas obtained from the decomposition of, e.g., sewage [93], organic municipal waste [94,95], animal faeces [96], agricultural and food industry waste [97,98] and plant materials [96,97,99], can be used by plants processing these materials to propel their machinery and equipment [100,101].…”

Biogas impurities: environmental and health implications, removal technologies and future perspectives

“…Due to the convenience and adaptability of use, biogas can be an opportunity for both developing and developed countries in terms of reduction of fossil fuel dependent energy supply, mitigating the effect of climate change and reduction of greenhouse gas emissions. Besides, biogas is an attractive alternative energy supply pathway for those countries that have a strong dependency on fossil fuel energy supply ( Macor and Benato, 2020a ).…”

“…Accordingly, if biogas is not treated for the removal of its impurities (prior to its high value applications), the heat value of biogas will drop (due to its lower calorific value during combustion by reducing the biogas methane content) and these impurities will cause environmental impacts ( Paolini et al., 2018b ) and health concerns ( Macor and Benato, 2020a , 2020b , 2021 ). Different public health concerns (like pulmonary paralysis, asthma, respiratory diseases, the spread of communicable diseases and deaths) and various environmental impacts (such as global warming, climate change and their indirect impacts like drought, flooding, malnutrition, and other disasters) have been reported ( Macor and Benato, 2020a , 2020b , 2021 ) ( Table 2 ). According to the Health Impact Assessment (HIA) explained by Macor and Benato (2021) , the biogas impurities, NOx, SOx, volatile organic compounds (VOC) and CO contributes to 91, 6.5, 1.4 and 0.7%, respectively to damage human health.…”

“…A complete removal of carbon dioxide and other impurities is essential to enhance the biogas quality into biomethane ( Nguyen et al., 2020 ) and to withdraw the revealed impacts. The need for biogas pretreatment is not only to address the aforementioned issues ( Macor and Benato, 2020a , 2021 ), but also to increase its calorific value for use in high-value applications by converting it to biomethane (a quality equivalent to natural gas) ( López et al., 2012 ). Therefore, there is a need to apply sustainable technologies based on economic, environmental, and health implications of biogas.…”

New Carvone-Based Deep Eutectic Solvents for Siloxanes Capture from Biogas

“…Biogas mainly consists of methane (CH 4 ) and carbon dioxide (CO 2 ). In addition, biogas contains a lot of impurities including inorganic gaseous compounds, i.e., nitrogen, oxygen, hydrogen, ammonia, carbon monoxide and water vapor, and numerous volatile organic compounds (VOC), including sulfur, nitrogen, oxygen-containing compounds, siloxanes, terpenes, linear and aromatic hydrocarbons [8][9][10]. The total concentration of organic and inorganic impurities may even amount to 65% of the volume of the obtained biogas, constituting a ballast that significantly reduces its calorific value.…”