The project is investigating the technical and commercial viability of bioDICE – a renewables technology which could to provide near-zero net greenhouse gas emissions, be cost competitive with wind or PV power generation and offer dispatchable or 24×7 power production.
BioDICE involves producing a char-water slurry (a micronised refined carbon, or MRC) from biomass and using this to fuel large adapted diesel engine generators – which are the most efficient and fuel flexible of all electrical generation technologies, and available in smaller capacities highly suited for distributed electricity generation.
Biomass > Low temperature carbonisation > Water-based slurry fuel (MRC) > Ultra efficient diesel engine generation (DICE)
Schematic of the bioDICE fuel cycle.
The project is investigating the use of low-temperature carbonisation (or torrefaction) of forest and mill wastes to produce chars suitable for fine milling to make slurries suitable for injection into diesel engines – in a similar manner to fuel oil. Other key objectives are to determine the overall process efficiency and economics relative to current utilisation technology (firing biomass into steam boilers) and to identify a development pathway for commercialisation of the technology.
The fuel production work has been the main focus of Stage 1 of the work, to determine the best conditions to produce a stable, injectable fuel with the highest possible specific energy and lowest possible viscosity – and with the highest possible overall energy conversion efficiency from biomass.
Early results using Pine and Nitens biomass, have shown that a processing temperature of around 320°C is enough to enable fine milling of the char. In addition, that all condensible fractions from carbonisation or torrefaction can be added back into the char and slurry to increase energy conversion to MRC and with the added benefit of preventing microbial degradation of the MRC slurry fuel.
Mould colonies on MRC after 3 days without condensibles.
MRC after 205 days with condensibles.
Process modeling shows that engine waste heat from the cooling system and exhaust are in excess of that required for biomass drying and carbonisation of the biomass feed, and gives a projected overall thermal efficiency for a 3.5 MW plant of around 34% (LHV basis), with over 40% projected for larger units.
Work is progressing to undertaken duration testing of a prototype ceramic injector nozzle (essential for slurry fuels), to obtain data for combustion performance in a laboratory test engine, and to obtain plant costings to develop a case for commercialisation. Work has also started on designing a larger fuel injection system suitable for a megawatt scale engine with a Chinese engine manufacturer.
