Thermal characterization of blends of faecal sludge and lignocellulosic biomass to produce biochar

Treatment of faecal sludge using pyrolysis can produce biochar with low heating value. The blending of faecal sludge with lignocellulosic biomass during pyrolysis can increase the heating value and also produce better quality biochar yield which is desirable for biofuels. The objective of the study is to investigate the kinetic behaviour of faecal sludge and lignocellulosic biomass blends during pyrolysis for biochar production. The samples of beech wood and VIP toilets were blended together and used as feedstock to assess the kinetic behaviour using TGA. These blends were further characterised by assessing the volatile matter, ash content and heating value prior to testing. The blend residue after the TGA was also assessed by analysing the inorganic elements. The blend mass ratios of the beech wood and VIP toilets samples consisted of 50% beech wood (BW) and 50% VIP (V), 30% BW and 70% V, 70% BW and 30% V, 20% BW and 80% V. The kinetic behaviour of blends was carried out using simultaneous TGA-DSC analysis. The blend samples were 4-6mg and below 300μm in size. The sample were heated up to a temperature of 900°C at a rate of 3°C/min under pure grade 6 N2 at 50mL/min. The results demonstrated that the kinetic behaviour of blends of VIP toilets and beech wood seems additive during pyrolysis. Furthermore, blending of VIP toilet sludge with beech wood increases the heating value. There was evidence of inorganic elements migration from the TGA residue between the two blends. However, there was no visible effect on the kinetic behaviour of the blends during pyrolysis. Further tests need to be done to assess the composition of VIP toilets to assess how these affect pyrolysis kinetics