Effect of Pasteurisation on Methane Yield from Food Waste and Other Substrates in Anaerobic Digestion

Abstract

The effect of pasteurisation and co-pasteurisation on biochemical methane potential values in anaerobic digestion (AD) was studied. Pasteurisation prior to digestion in a biogas plant is a common hygienisation method for organic materials which contain or have been in contact with animal by-products. Tests were carried out on food waste, slaughterhouse waste, animal blood, cattle slurry, potato waste, card packaging and the organic fraction of municipal solid waste (OFMSW); pasteurisation at 70 °C for 1 h was applied. Pasteurisation had increased the methane yields of blood (+15%) and potato waste (+12%) only, which both had a low content of structural carbohydrates (hemi-cellulose and cellulose) but a particularly high content of either non-structural carbohydrates such as starch (potato waste) or proteins (blood). With food waste, card packaging and cattle slurry, pasteurisation had no observable impact on the methane yield. Slaughterhouse waste and OFMSW yielded less methane after pasteurisation in the experiments (but statistical significance of the difference between pasteurised and unpasteurised slaughterhouse waste or OFMSW was not confirmed in this work). It is concluded that pasteurisation can positively impact the methane yield of some specific substrates, such as potato waste, where heat-treatment may induce gelatinisation with release of the starch molecules. For most substrates, however, pasteurisation at 70 °C is unlikely to increase the methane yield. It is unlikely to improve biodegradability of lignified materials, and it may reduce the methane yield from substrates which contain high contents of volatile components. Furthermore, in this experimental study, the obtained methane yield was unaffected by whether the substrates were pasteurised individually and then co-digested or co-pasteurised as a mixture before batch digestion.

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 is a mixture of gases characterized by a varied composition, but it can be purified to bio-methane and then meet the quality standards of natural gas [102].…”

Estimating the Methane Potential of Energy Crops: An Overview on Types of Data Sources and Their Limitations

“…This can be as short as 50 days for substances such as cellulose [23] or may take 100 days or more for some cropbased materials due to their lignocellulosic content [32]. In a recent attempt to standardise BMP tests, it is recommended that the test is terminated when the daily net methane production during three consecutive days is less than 1% of the accumulated methane produced from the substrate already [24,31], although the duration of the test should also be taken into consideration for unexpected degradation patterns or inhibition effects [33]. The inoculum must necessarily be digested separately (under the same conditions) to obtain a control value (amount of methane produced by the inoculum only); this control value must be deducted from the results of the test vessels to obtain the yield attributed to the actual test substrate.…”

Effects of different treatments of manure on mitigating methane emissions during storage and preserving the methane potential for anaerobic digestion

“…Pasteurization is traditionally used to suppress microbial activity, which is why it might be useful in suppressing CH 4 emissions. Zhang et al (2020) further showed that pasteurization can increase the CH 4 yield of some specific substrates during anaerobic digestion. Furthermore, it can relatively easily be applied on pig farms or in biogas plants, especially if coupled with a manure heat exchanger system, as described in two pending patents (Henriksen et al, 2021a;2021b).…”