The potential of biogas production from fish waste as source of renewable energy for fishermen communities was evaluated. Four different fish waste concentrations (1%, 1.5%, 2% and 2.5% total solids (TS)) were digested during 28 days at mesophilic conditions. Biochemical Methane Potential (BMP), volatile fatty acids (VFA) concentration and ammonia concentration were analysed during the experiment. Energy production and economic projections were performed to estimate the number of families that can benefit from the biogas production in Tumaco, Colombia. The 1% TS had the highest BMP (464.5 mL CH4/g VS) and the lowest VFA production (2515 mg/L); in contrast, the 2.5% TS had the highest VFA production (11302 mg/L

The potential to recover bioenergy from anaerobic digestion of water hyacinth (WH) and from its co-digestion with fruit and vegetable waste (FVW) was investigated. Initially, biogas and methane production were studied using the biochemical methane potential (BMP) test at 2 g volatile solids (VS) L(-1) of substrate concentration, both in the digestion of WH alone and in its co-digestion with FVW (WH-FVW ratio of 70:30). Subsequently, the biogas production was optimized in terms of total solids (TS) concentration, testing 4 and 6% of TS. The BMP test showed a biogas yield of 0.114 m(3) biogas kg(-1) VSadded for WH alone. On the other hand, the biogas potential from the WH-FVW co-digestion was 0.141 m(3) biogas kg(-1) VSadded, showing an increase of 23% compared to that of WH alone. Maximum biogas production of 0.230 m(3) biogas kg(-1) VSadded was obtained at 4% of TS in the co-digestion of WH-FVW. Using semi-continuously stirred tank reactors, 1.3 m(3) biogas yield kg(-1) VSadded was produced using an organic loading rate of 2 kg VS m(-3) d(-1) and hydraulic retention time of 15 days. It was also found that a WH-FVW ratio of 80:20 improved the process in terms of pH stability. Additionally, it was found that nitrogen can be recovered in the liquid effluent with a potential for use as a liquid fertilizer.

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Screenings produced as the first stage of wastewater treatment and currently disposed of to landfill, are rich in volatile organic solids, nitrogen and phosphorus which could be recovered through anaerobic digestion. Biochemical methane potential (BMP) tests on screenings demonstrated a methane yield of 0.33 m3 methane/kg volatile solids (VS) and a VS destruction of 50%. Consequently, the effect of a range of hydraulic retention time (HRT) and organic loading rates (OLRs) was evaluated in lab‐scale continuously fed mesophilic digesters. The highest methane yield of 0.416 Nm3 methane/kg VS added was observed with an HRT of 15 days and an OLR of 2.5 kg VS/m3/day, when up to 65% of the VS were destroyed. If treated by anaerobic digestion, every dry tonne of screenings digested would divert 466 kg from landfill, save 4.6 tonne equivalent carbon dioxide (CO2 eq) and deliver 3.4 MWh of renewable energy.

Anaerobic biodegradability and hydrolysis rates of wastewater screenings were determined using the biochemical methane potential test at 37 °C. The extent and rate of screenings conversion to methane of this complex and particulate substrate were investigated and since two stages of hydrolysis were identified, corresponding to the different types of materials in screenings, a linear and non-linear model was used. No accumulation of intermediary products was observed and so it was possible to use the methane production rate and a linear model to estimate the hydrolysis rate in the first phase of hydrolysis. The measured values of 0.061-0.127 d(-1) are in the range reported for other comparable organic wastes. It was also observed that the inoculum-to-substrate ratio has a large impact on methane production rate of screenings. The difference in biodegradation rates from the materials in screenings and the overall hydrolysis could be represented by the modified Gompertz non-linear model which was able to describe the methane production rate of screenings with a high confidence. Screenings were found to have 52% biodegradability on average and this shows the potential for volatile solids destruction. A two-stage process with an improved hydrolysis rate is proposed to ensure that the full potential of the material is exploited.