Calorimetric investigation of anaerobic digestion: Biomass adaptation and temperature effect

Abstract

A high-resolution bench-scale calorimeter (Bio-RC1), specially suited for microbiological studies, has been used to investigate the response of an anaerobic granular sludge to repetitive glucose additions at various temperatures. Through the analysis of heat-evolution profiles resulting from substrate degradation, significant biological events have been identified: the feeble net heat uptake related to aceticlastic methanogenesis has been evaluated, and the detrimental effect of a nutrient deficiency, which led up to 75% decrease in heat production rate, has been detected. After several glucose pulses under non-limiting nutrient conditions, a reliable and reproducible reference thermal response, which is an important condition for the application of calorimetric measurements to detect inhibitory effects, was finally obtained. Afterward, glucose additions were repeated at various temperatures, and 57% biomass activity reduction, with respect to the reference value at 35 degrees C, was observed when temperature was fixed at 20 degrees C. Additionally, a preliminary toxicity test was also performed by exposing the biomass to increasing formaldehyde concentrations.

Prediction of temperature and thermal inertia effect in the maturation stage and stockpiling of a large composting mass

“…One of the main problems which hinders a reliable energy balance performance is the difficulty to obtain accurate measures of heat generation, especially when complex microbial communities interact (Daverio et al, 2003). Respiration indices have been routinely used in the monitoring of composting process to quantify the global biological activity or to determine the stability of compost (Ianotti et al, 1993;Scaglia et al, 2000;Adani et al, 2003;Gea et al, 2004).…”

Recent Developments in Bio-Energy Recovery Through Fermentation

“…The exothermic carbohydrate degradation and the high energy density in the substrates, together with high loading rates, can cause a sudden temperature increase. Such self-heating effects led to an increase in process temperatures from 35-39 C to 42-49 C (Daverio et al 2003;Lindorfer et al 2006;Braun 2007). This effect was accompanied by a gradual cease in methane formation.…”

“…Due to the high variation of substrates applied in methane fermentations, several other environmental impacts can affect methane formation. Especially, substrates with high volatile solid (VS) contents (e.g., energy crops) can cause an upset through sudden temperature increase (Daverio et al 2003;Lindorfer et al 2006;Braun 2007). Even a lack in trace element supply may occur with some substrates (Hummer 2006) used in methane fermentations (e.g., exhaust vapor condensate, energy crops).…”

Bioaugmentation enhances dark fermentative hydrogen production in cultures exposed to short-term temperature fluctuations

“…Dark fermentative H 2 production can be carried out at mesophilic, thermophilic and hyperthermophilic conditions (Shin et al 2004;Kargi et al 2012) but is thermodynamically more favourable at higher temperatures (Zhang et al 2014;Zheng et al 2015). In addition, thermophilic bioprocesses typically result in higher H 2 production rates as well as inhibition of pathogens (Sahlström 2003) and H 2 consumers such as methanogens and homoacetogens (Dessì et al 2018b;Dessì et al 2018a). However, decreased bacterial diversity at higher temperatures can lead to instability of the bioprocess (Westerholm et al 2018).…”