Application of waste from biodiesel synthesis for the production of fuel pellets and biogas

The enzymatic process of simultaneous oil extraction and interesterification (in situ) using methyl formate as acyl receptor can be applied for biodiesel synthesis. This process produces waste (a mixture of rapeseed cake and enzymatic catalyst), which is suitable for energy purposes-production of fuel pellets and biogas. Fuel pellets were produced using hemp seed husks and waste from the interesterification, the amount of which in the mixture with hemp husks ranged from 0 to 25%. The optimal composition of raw materials and the physical and chemical properties of the resulting fuel pellets were determined. It was found that pellets produced using interesterification waste without mineral diesel fuel were durable, and their durability increased with increasing the content of waste, while the pellets produced using an interesterification waste containing mineral diesel residues were unstable, but had a higher calorific value. It was proposed to use the biodiesel production waste for anaerobic digestion pure or by mixing it up to 30% with sewage sludge. The research results showed that the biogas yield from the mixture of biodiesel synthesis waste with sewage sludge is higher than from pure sewage sludge conventionally used for biogas production. The obtained biogas produced using biodiesel production waste contained more than 66% of methane. Rapeseed meal increases the biogas yield, but mineral diesel residues in the biodiesel production waste have a negative effect on biogas-producing bacteria.