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Lignocellulosic rice processing residue was pretreated in liquid hot water (LHW) at three different temperatures (140, 160, and 180 °C) and two pretreatment times (10 and 20 min) in order to assess its effects on hydrolysates composition, matrix structural changes and methane yield. The concentrations of acetic acid, 5-hydroxymethylfurfural and furfural increased with pretreatment severity (log Ro). The maximum methane yield (276 L kg−1 VS) was achieved under pretreatment conditions of 180 °C for 20 min, with a 63% increase compared to untreated biomass. Structural changes resulted in a slight removal of silica on the upper portion of rice husks, visible predominantly at maximum severity. However, the outer epidermis was kept well organized. The results indicate, at severities 2.48 ≤ log Ro ≤ 3.66, a significant potential for the use of LHW to improve methane production from rice processing residue.

Poultry litter (PL) is one of the drier and bulkier manures produced in intensive agriculture. Land spreading is considered the most common treatment option for PL; however, this causes large atmospheric greenhouse emissions and consequently a high negative environmental impact. PL has several factors that limit its sustainable use as an energy source, and thus there is still a need for more studies about sustainable waste management. The paper aims at: (i) proposing sustainable pathways in order to maximise the PL valorisation process, based on previous experiences described in the literature; and (ii) showing the advantages of reforming poultry farms into biorefineries in Cuba. Combinations of techniques are used to increase PL valorisation, but only by modulating the theoretical data has an improvement occurred. In this work, pathways for thermo‐ and bioconversion processes are proposed which involve four major technologies for converting PL into useful energy and fertiliser, being pyrolysis/gasification, hydrothermal carbonisation and anaerobic digestion as key conversion technologies. Including technologies for nutrient recovery in the proposed pathways would allow better agricultural applications. The treatment of PL in biorefineries in Cuba would have a positive impact on the economy through income generation and savings resulting from reductions in imports (i.e. fossil fuels and agrochemicals), employment creation, improved living conditions and development in rural communities. Future studies should be aimed at evaluating the various proposed pathways in order to maximise the PL valorisation process, in addition to a marketing study of the products generated through the biorefineries at poultry farms. © 2020 Society of Chemical Industry (SCI)