by Jim Lane (Biofuels Digest) At the frontier of exotic temperature and pressures, even everyday materials like water begin to act strangely in ways that can drive energy transformation. New work in nanocatalysts may make those frontiers more accessible, and those energy systems more affordable.
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As is not commonly discussed around the breakfast table, water has far more than the three traditional phases we know from life (ice, liquid water and steam). In fact, science has presented us with fifteen distinct phases, to date.
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Another boundary that becomes ill-defined under sufficient temperature and pressure — and that impacts the here and now of biofuels — that’s the gas-liquid boundary.
At a well-known “supercritical” point – at 374 degrees Celsius and 221 atmospheric pressures – the boundary between liquid water and steam becomes ill-defined and “supercritical water” begins to act as excellent solvent for cellulose — separating C6 sugars from lignin in seconds, compared to the hours or days associated with enzymatic systems.
The exploration of supercritical water as a biofuels technology is at the heart, as it happens, of the Renmatix Plantrose system — producing a stream of C5 and C6 sugars, plus a lignin fraction — at what it believes, at scale, will be industry-transforming low costs. Renmatix is building towards that scale right now.
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But even when the science is done — there’s the cost of creating all that energy and pressure. Now, lignin contributes to providing that, through combustion of that residual fraction — that’s part of why Renmatix is looking at transformatively low-cost sugars with its system.
But, with high temperature and pressure, you not only have operating costs to consider in terms of delivering system energy — you have capital costs associated with materials that can withstand high temps and pressures. Not every steel alloy can handle it, plastics are a no-no, and valves and flanges will generally need to be of the high-performance type.
Not exactly building the Space Shuttle, but it’s a walk down the Deadly Path of High Cost, for sure.
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One group, ECR Renewable Fuels and Georgia Alternative Fuels, has been pursuing nanocatalysts and their effect on supercritical boundaries for several years. The goal? To reduce the temperature and pressure barrier at which liquids begin to demonstrate supercritical properties — using catalysis to reduce the energy levels.
“Our cellulosic ethanol process uses the supercritical heterogeneous catalytic process to pretreat cellulose,” said Alan Lawson, who heads the group. At a pilot and lab-scale, the technology is modeling along exciting lines.
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As seen at lab and pilot-scale, Lawson says, “The process lowers our costs significantly to make a small scale system produce a very nice profit. We can now compete with mid-west ethanol on the East Coast. Our per pound sugar cost using biomass is about $0.04 per pound verses $0.125 per pound for corn ethanol. Our model is small cellulosic ethanol plants highly distributed over the East, at less than 10 million gallons per year.”
The practical effect of using supercritical to replace enzymes in the process and going smaller-scale? Lower costs, if the system develops towards scale as hoped.
“Small scale production costs are currently less than $1.40 per ethanol gallon. Using local market sources within a couple miles of the plant, we project to rubber stamp the small scale plants for sale to co-op farmers that can fund our small scale plants, with about a 1.5 year payback.”
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On the drop-in side? “We are now looking into using waste coal from exiting slurry ponds,” Lawson says, adding that “gas well liquids, biomass, waste solids from cities and other sources” are options as well. READ MORE and MORE (US Patent and Trademark Office)