Green job bio-aerosol exposure during anaerobic digestion for biomass energetic valorisation

Analysing the Impact on Health and Environment from Biogas Production Process and Biomass Combustion: A Scoping Review

The increasing demand for renewable energy production entails the development of novel green technologies, among them the use of biomass for energy generation. Industrial processes raise new issues regarding emerging risks for the health of people working in biogas plants and of nearby communities. The potential epidemiological and environmental impacts on human health related to biogas plants were assessed by means of a review of the available literature. Nineteen papers published between 2000 and 2022 were identified through electronic database search using search strings. The selected works are epidemiological studies and environmental monitoring studies, which aimed at investigating what are the health risk factors for biogas plant workers and for people living in the surrounding communities. The results of the epidemiological studies revealed a potential exposure to endotoxins and fungi that are associated with respiratory symptoms. Furthermore, the results from the environmental monitoring studies showed significant concentrations of particulate matter, microbial agents, endotoxins, and VOCs in occupational settings. In conclusion, the results of this literature review suggest that further analyses through an integrated approach combining environmental and health data are necessary for a comprehensive understanding of the potential risks associated with the uptake of biogas technology.

Anaerobic digestate management, environmental impacts, and techno-economic challenges

Digestate is a nutrient-rich by-product from organic waste anaerobic digestion but can contribute to nutrient pollution without comprehensive management strategies. Some nutrient pollution impacts include harmful algal blooms, hypoxia, and eutrophication. This contribution explores current productive uses of digestate by analyzing its feedstocks, processing technologies, economics, product quality, impurities, incentive policies, and regulations. The analyzed studies found that feedstock, processing technology, and process operating conditions highly influence the digestate product characteristics. Also, incentive policies and regulations for managing organic waste by anaerobic digestion and producing digestate as a valuable product promote economic benefits. However, there are not many governmental and industry-led quality assurance certification systems for supporting commercializing digestate products. The sustainable and safe use of digestate in different applications needs further development of technologies and processes. Also, incentives for digestate use, quality regulation, and social awareness are essential to promote digestate product commercialization as part of the organic waste circular economy paradigm. Therefore, future studies about circular business models and standardized international regulations for digestate products are needed.

Multiplexed Workplace Measurements in Biogas Plants Reveal Compositional Changes in Aerosol Properties

Anaerobic digestion is an emerging technology producing energy from renewable resources or food waste. Exposure screenings, comprising hazardous substances and biological agents, at different workplaces are necessary for a comprehensive overview of potential hazards in order to assess the risk of employees in biogas plants. In order to analyse these parameters, workplace measurements were conducted in seven full-scale anaerobic digesters. Personal and stationary sampling was performed for inhalable and respirable particles, volatile organic compounds, ammonia, hydrogen sulphide, carbon monoxide, and carbon dioxide. Furthermore, concentrations of the total cell count, endotoxins, and fungi-down to species level-were determined in comparison to windward air. Sequencing of the 16S rRNA genes was utilized for the determination of the bacterial composition inside the biogas plants. Measurements of hazardous substances show hardly values reaching the specific occupational exposure limit value, except ammonia. An approximate 5-fold increase in the median of the total cell count, 15-fold in endotoxins, and 4-fold in fungi was monitored in the biogas plants compared with windward air. Specifying the comparison to selected workplaces showed the highest concentrations of these parameters for workplaces related to delivery and cleaning. Strikingly, the fungal composition drastically changed between windward air and burdened workplaces with an increase of Aspergillus species up to 250-fold and Penicillium species up to 400-fold. Sequence analyses of 16S rRNA genes revealed that many workplaces are dominated by the order of Bacillales or Lactobacillales, but many sequences were not assignable to known bacteria. Although significant changes inside the biogas plant compared with windward air were identified, that increase does not suggest stricter occupational safety measures at least when applying German policies. However, exposure to biological agents revealed wide ranges and specific workplace measurements should be conducted for risk assessment.

Sources of Airborne Endotoxins in Ambient Air and Exposure of Nearby Communities—A Review

Endotoxin is a bioaerosol component that is known to cause respiratory effects in exposed populations. To date, most research focused on occupational exposure, whilst much less is known about the impact of emissions from industrial operations on downwind endotoxin concentrations. A review of the literature was undertaken, identifying studies that reported endotoxin concentrations in both ambient environments and around sources with high endotoxin emissions. Ambient endotoxin concentrations in both rural and urban areas are generally below 10 endotoxin units (EU) m−3; however, around significant sources such as compost facilities, farms, and wastewater treatment plants, endotoxin concentrations regularly exceeded 100 EU m−3. However, this is affected by a range of factors including sampling approach, equipment, and duration. Reported downwind measurements of endotoxin demonstrate that endotoxin concentrations can remain above upwind concentrations. The evaluation of reported data is complicated due to a wide range of different parameters including sampling approaches, temperature, and site activity, demonstrating the need for a standardised methodology and improved guidance. Thorough characterisation of ambient endotoxin levels and modelling of endotoxin from pollution sources is needed to help inform future policy and support a robust health-based risk assessment process.

The Use of Biomass for Electricity Generation: A Scoping Review of Health Effects on Humans in Residential and Occupational Settings

The utilization of biomass for power generation has become more prevalent globally. To survey the status of evidence concerning resulting health impacts and to depict potential research needs, a scoping-review was conducted. Biomass life cycle phases of interest were the conversion and combustion phases. Studies from occupational and residential settings were considered. The scoping review was conducted systematically, comprising an extensive literature search, a guided screening process, in-duplicate data extraction, and critical appraisal. Two reviewers executed most review steps. Nine articles of relevance were identified. In occupational settings of biomass plants, exposure to endotoxins and fungi might be associated with respiratory disorders. An accidental leakage of hydrogen sulfide in biogas plants may lead to fatalities or severe health impacts. Living near biomass power plants (and the accompanied odorous air pollution) may result in an increased risk for several symptoms and odor annoyance, mediated by perception about air pollution or an evaluation of a resulting health risk. The methodological quality of included studies varied a lot. Overall, the body of evidence on the topic is sparse and future high-quality research is strongly recommended.