A pig slurry feast/famine feeding regime strategy to improve mesophilic anaerobic digestion efficiency and digestate hygienisation

Abstract

The increasing concentration of livestock farms results in large amounts of waste production and the need for their management. The study of anaerobic digestion (AD) technology, under mesophilic conditions, applied to pig slurry is of the upmost importance for biogas recovery and sanitised digestate, contributing to a circular economy. The assessment of the effects of a feast/famine regime on biogas and biomethane (bio-CH4) yield with different feeding frequencies was performed. The evaluation was made in regards to three scenarios: the first is based on daily feeding (FR1); in the second, the feeding occurs once every two days (FR2); and in the third, the feeding happens once every three days (FR3). The results demonstrate that the biogas and methane yield increased by 34% and 37% between FR1 and FR3. The stability inside the reactor was maintained since specific loading energetic rate values did not exceed the recommended limit (0.4 d−1). It was also possible to conclude that the AD technology was efficient to sanitise the pig slurry, with the count of Escherichia coli going from 1 × 105 colony-forming units (CFU) g−1 to less than 100 CFU g−1, meeting the legal requirements for agricultural valorisation. The total anaerobic mesophile plate counts were significantly ( p < 0.1) reduced from feeding to digestate, and the plate counts of Clostridia were significantly ( p < 0.05) increased, reflecting the changes in the composition of the microbiota. The increasing yield in bio-CH4 in accordance with Clostridium counts suggests this genus as a positive microbiological key indicator of the AD performance.

Energetic Valorization of Cereal and Exhausted Coffee Wastes Through Anaerobic Co-digestion With Pig Slurry

“…These values also indicate a good possibility of the digestate being used as a biofertilizer in the future, after being submitted to an organic amendment process to prevent nitrification of the soils (Sawada and Toyota, 2015). The results obtained by the authors are in accordance with Silva et al (2020) and Azevedo et al (2021), which performed similar AD trials and AcoD with PM with different co-substrates, in same operational conditions, such as HRTs and temperature.…”

“…The heating system comprises a heating stirring and feed control interface (inside there are four components: control board, solid state relays, normal relay, and communication interface with computer), and is controlled by a thermostat with an accuracy of ±0.5 • C, which served to keep the temperature range at 36.9 ± 0.3 • C. This value was based on previous studies developed and published by the authors, to enhance biogas and methane production for PS with other co-substrates (Silva et al, 2020;Azevedo et al, 2021).…”

A review of advances in valorization and post-treatment of anaerobic digestion liquid fraction effluent

“…The rise in fossil fuel prices combined with their limited resources and their impact on the environment motivates research towards alternative energy sources (Go et al, 2019; Martins das Neves et al, 2009; Silva et al, 2020). Many countries use alternative energy sources such as wind and solar power instead of fossil fuels.…”

“…AD is an advantageous process that targets renewable energy production in the form of biomethane. Consequently, this process reduces greenhouse emissions, decontaminates and reduces waste volume (Silva et al, 2020). The latter is important because many wastes end up in sanitary landfill sites or released into the environment.…”

A mini-review of biomethane valorization: Managerial and policy implications for a circular resource

“…The growing awareness of the need for safely restoring and valorizing waste and biomass to valuable materials and energy is turning up as a major trend for sustainable development (D’Adamo et al, 2022), able also to recovery and reuse additional products (Ferella et al, 2017). In detail, bioeconomy is defined as a paradigm capable to convert renewable energy resources (RES) biologically deriving from the land and sea – animals (Silva et al, 2020), water (Hildebrandt and Bezama, 2018), crops and agrowaste (Moustakas et al, 2020), forests, etc. – to energy (Fragoso et al, 2021), food (Ragossnig and Ragossnig, 2021) and materials (Lekkas et al, 2021).…”