Hygiene and Sanitation in Biogas Plants

Abstract

The increasing number of agricultural biogas plants and higher amounts of digestate spread on agricultural land arouse a considerable interest in the hygiene situation of digested products. This chapter reviews the current knowledge on sanitation during anaerobic digestion and the hygienic status of digestate concerning a multitude of pathogens potentially compromising the health of humans, animals and plants. Physical, chemical and biological parameters influencing the efficiency of sanitation in anaerobic digestion are considered. The degree of germ reduction depends particularly on the resistance of the pathogen of concern, the processing conditions, the feedstock composition and the diligence of the operation management. Most scientific studies facing sanitation in biogas plants have provided data ascertaining reduction of pathogens by the biogas process. Some pathogens, however, are able to persist virtually unaffected due to the ability to build resistant permanent forms. As compared to the feedstock, the sanitary status of the digestate is thus improved or in the worst case, the sanitary quality remains almost unchanged. According to this, the spreading of digestate on agricultural area in accordance to current rules and best practice recommendations is considered to impose no additional risk for the health of humans, animals and plants.

Is anaerobic digestion a reliable barrier for deactivation of pathogens in biosludge?

“…It had been reported that about 6.5 million metric ton (dry weight) of sewage sludge were generated annually, in which waterborne pathogens may be concentrated substantially (Shen et al, 2015). As such, biosolid disposal sites might act as the sources of pathogens, leading to a potential risk of uncontrollable spread into surface water, ground water and soils (Fröschle et al, 2015a(Fröschle et al, , 2015b. Without proper control, sludge-associated pathogens could continue to grow, causing potential threats to the human health.…”

Fate of Clostridium botulinum and incidence of pathogenic clostridia in biogas processes

“…The presence and behaviour of diverse human, animal and plant pathogens was addressed in a series of studies as recently reviewed (Franke-Whittle and Insam 2013; Avery et al 2014;Fr€ oschle et al 2015;Insam et al 2015). The presence and behaviour of diverse human, animal and plant pathogens was addressed in a series of studies as recently reviewed (Franke-Whittle and Insam 2013; Avery et al 2014;Fr€ oschle et al 2015;Insam et al 2015).…”

Rural Urban Sustainability in Malinalco, Mexico

“…The digestate could be used as manure as an alternative to raw feces, limiting the spread of pathogens [5].…”