CelloFuel Portable Biomass Refinery

We develop the CelloFuel Portable Biomass Refinery, for producing low-carbon bioethanol from sugarcane, sweet sorghum and softwood wood chips. Our goal is to make bioethanol at a lower cost than existing technologies while at the same time producing bioethanol with less carbon intensity. Key markets for ethanol are California, Germany, Sweden and Finland, which have a 70% higher market price for low-carbon bioethanol.

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Reduces CAPEX, OPEX and carbon intensity

We reduce the capital expenses (CAPEX) of producing bioethanol by:

  • using mass-produced HDPE (high density polyethylene) pipes
  • using mass-produced parts
  • using standard hand tools for assembly/disassembly
  • using existing farm equipment for loading and unloading biomass.
  • not using stainless steel
  • not using pressure vessels
  • not using a separate distillation column

Our goal is a CAPEX of less than $1 per gallon/year for ethanol from sugarcane and sweet sorghum, which is less than that of a modern corn ethanol plant. Our goal is a CAPEX of less than $2 per gallon/year for ethanol from softwood wood chips, which is significantly less than that of lignocellulosic ethanol plants.

We reduce the operating expenses (OPEX) and carbon intensity of producing bioethanol by:

  • not transporting biomass - by producing bioethanol near the source of the biomass
  • not separating sugars from biomass - by using yeast infusion instead of energy-intensive extraction technologies
  • producing fertilizer - by using residues to fertilize land

Technology summary

The CelloFuel Portable Biomass Refinery produces bioethanol from carbohydrate-rich biomass by:

  • Impregnating sugarcane/sweet sorghum with yeast using US Patent 9,631,209
  • Filling size-reduced biomass into vertical HDPE pipes from the top
    • Sugarcane/sweet sorghum - commercial sugarcane shredders
    • Softwood forestry residues - commercial wood chippers and auger bucket
  • Softwood - dilute oxalic acid hydrolysis of hemicellulose at 95 C for 48 hours, neutralization with calcium hydroxide, solid state fermentation with yeast
  • Distilling in HDPE pipes using US Patent 10,087,411
  • Emptying residual biomass from vertical HDPE pipes by pivoting about the center of gravity using a trunnion
  • Returning residual biomass to fields as fertilizer (or air-drying and burning for distillation energy)

Produces hydrous ethanol

The CelloFuel modules produce hydrous ethanol at 80% to 95% Alcohol By Volume (ABV). This can be used to produce potable ethanol, fuel for motors and fuel for cooking. This hydrous ethanol can be transported to a central refinery for further production of transportation fuels or higher-value chemicals.

Mechanical design

The CelloFuel Portable Biomass Refinery is made from multiple CelloFuel modules, each made of a vertical HDPE pipe. There are a variety of options for loading the HDPE pipes - screw conveyers, conveyer belts, front-loaders, vacuum conveying, etc.

The top and bottom of the HDPE pipe are joined with steel plates coated with fusion bonded epoxy, or alternatively type 444 stainless steel. The top cap circulates water for a distillation dephlegmator. The top and bottom caps are joined to the HDPE pipe with a gasket. The top cap can be lifted off the HDPE pipe for biomass loading and unloading. An induction heater or steam heater is used to apply heat to the bottom cap. HDPE, fusion bonded epoxy and type 444 stainless steel are all resistant to corrosion by oxalic acid.

Multiple HDPE pipes are mounted in rows so that they can be loaded and unloaded efficiently. The loading time is 5 to 30 minutes, depending on whether the biomass is being size-reduced while loading. The unloading time is 5 minutes and the processing time is 3 to 4 days, so the time spent loading and unloading is a small fraction of the total time.

Safety and Environment

When using steam or 95 C water, one should be careful of a failure that leads to pressure build-up in the HDPE pipe leading to an explosion. The top cap is fairly heavy (50 kg) and is held onto the top of the HDPE pipe with gravity. If there's an unexpected steam pressure build-up, the top cap raises up and releases steam.

When performing dilute oxalic acid hydrolysis with 0.110 M oxalic acid the pH is 1.2. A leak of this oxalic acid solution can easily be neutralized with a dilute solution of calcium hydroxide and the resulting calcium oxalate is biodegradable. Calcium hydroxide is also very safe to handle.

Burning biomass that has been infused with oxalic acid and calcium hydroxide is environmentally friendly, since this only releases CO2 and water vapor to the atmosphere.


The top cap can be winched to the ground for maintenance. The various connections to the HDPE pipe are easily accessible.

Reduces scale-up risk

A CelloFuel module is a single vertical HDPE pipe rotated about the center of gravity with a trunnion. Scaling up to larger scales involves simply replicating the HDPE pipes and in arrays.

Project Status (December 12, 2018)

We are doing lab-scale tests of dilute oxalic acid hydrolysis with this test apparatus:

CelloFuel Lab-Scale Apparatus

The pilot-scale HDPE pipes have been received. We are currently building a trunnion to hold and rotate the pipe. We've tested the HDPE pipe with a steel bottom cap and an induction heater.

We're building a prototype of the pilot-scale reactor which is scalable to HDPE pipes up to 1 m in diameter and 6 m high. The bottom cap, induction heater, and top cap have been integrated, sealed with 4 mm SBR gaskets. We applied 1800 W of heat with the induction heater, and found the heat loss was as predicted. We're looking into the best type of insulation needed (probably closed cell polyisocyanuranate).

Patent Status

There are two families of CelloFuel patents that have been granted in the US and around the world, including the EU, Canada, Russia, China and Brazil. We are now licensing these technologies and providing engineering consulting for profitable implementation of these technologies.

  • Method for fermenting stalks of the Poaceae family
  • Methods and apparatus for separating ethanol from fermented biomass
    • US10087411 (USA) status: Granted
    • Filed with India patent office
    • In process with EU, Canada, Russia, Ukraine, Brazil, Mexico, and China patent offices

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