Gasification of cotton crop residues for combined power and biochar production in Mozambique

•Cotton residues briquettes are a suitable fuel for small scale biomass gasifiers.•Experimental tests confirm efficiency values in line with wood chips gasification.•Biochar from gasification is a powerful soil admenant for cotton plants.•Biochar production and use establish carbon negative processes in rural areas.•Cotton residues gasification represents the basis for local circular economy models. Cotton agricultural industry is an important sector for some developing countries, whose energy consumption is dramatically rising. Here, biomass is the most important source of energy, but they are used in an inefficient way, causing atmospheric pollution and wasting resources. Combined energy generation and biochar production using cotton residues briquettes as fuel in a PP20 gasifier plant is investigated. The machine has demonstrated similar performances to its “conventional” use: 14% global efficiency and 1.16 kg/kWhel specific consumption of cotton briquettes are observed. It is calculated that one-hectare field can generate more than 4 MWh and about 130 kg of biochar per year. Biochar represents a valuable by-product; if used as amendment for cotton growth it can improve the soil conditions, both decreasing the need of fertilizers up to 50%. A circular economic model based on cotton waste gasification is proposed. Clean and affordable energy can be produced, in order to promote a sustainable development of rural areas.