Biomass Pyrolysis: Feedstocks & Rotary Kiln Technology

Biomass Pyrolysis

Biomass pyrolysis in an indirectly heated rotary kiln yields biochar, syngas and bio-oil from a single feedstock stream.

Pyrolysis is thermal conversion without oxygen. Feed biomass into a sealed, heated vessel and it does not burn; it decomposes. The volatile fraction leaves as gas and condensable vapour, and the fixed carbon stays behind as char. Control the temperature profile and the residence time and you control how much of the feedstock reports to each of the three product streams.

Why an indirectly heated rotary kiln

Indirect heating keeps the combustion gases outside the process. Nothing dilutes the syngas, nothing contaminates the char, and the energy input is controllable independently of what the feedstock happens to be doing. The rotary geometry handles the awkward part of biomass — variable particle size, variable moisture, variable density — by tumbling it continuously through the heated zone. That tolerance is what makes real-world residues processable rather than theoretical.

Feedstocks

Agricultural and forestry residues are the obvious candidates: rice husks, nut shells, straw, bark, sawdust, mill waste, prunings and clean wood. Rice husk deserves a specific mention, because the resulting biochar carries high silica content and high porosity, giving it value in soil, wastewater treatment and industrial applications. Each feedstock produces a different char, a different gas and a different bio-oil, so feedstock characterisation is the first engineering deliverable, never an afterthought.

Fixed plants and mobile units

Where feedstock is concentrated and an energy offtake exists, a fixed facility makes sense — Klean's 1 MW plant in Japan has run on that model since 2012. Where biomass is dispersed and transport economics kill the project, the answer is to move the reactor instead. A 40 tonne-per-day mobile biomass pyrolysis retort, MORPPS, has started operations in Vancouver to serve exactly that case.

Engineering the balance

Maximising char costs gas; maximising gas costs char. The right split is the one that matches the local value of carbon, electricity, heat and liquid fuel. Klean resolves that through feasibility studies and delivers the chosen configuration turn-key. Mass balances, yield curves and kiln sizing data are provided under NDA.