CelloFuel Portable Biomass Refinery

We develop the CelloFuel Portable Biomass Refinery, for producing low-carbon bioethanol from sugarcane, sweet sorghum, sugar beet 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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Technology Overview

The CelloFuel Portable Biomass Refinery has two parts, making ethanol-rich biomass using solid-state fermentation and extracting the ethanol using a patented biomass distillation column.

  • Sugarcane/sweet sorghum - impregnating with yeast using US Patent 9,631,209 or coating residual bagasse with yeast after squeezing out juice with a farm-scale press to make jaggery, cachaça or sweet sorghum syrup.
  • Sugar beet - coating size-reduced sugar beet chips with yeast
  • Softwood - dilute oxalic acid hydrolysis of hemicellulose at 95 C for 48 hours, neutralization with calcium hydroxide, solid state fermentation with yeast
  • Fermenting for 24 to 48 hours with air cooling
  • Filling vertical corrugated HDPE pipe with fermented biomass
  • Distilling in corrugated HDPE pipes using US Patent 10,087,411, producing >90% ethanol by volume (ABV)
  • Emptying residual biomass from vertical corrugated 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)

Reduces CAPEX, OPEX and carbon intensity

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

  • using mass-produced corrugated HDPE (high density polyethylene) pipes
  • using mass-produced parts
  • using standard hand tools for assembly/disassembly
  • 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

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. The pipes are loaded by rotating the pipe around its center of gravity on a trunnion.

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 cap can be lifted off the HDPE pipe for biomass loading and unloading. An induction heater, steam heater or hot oil 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.

Maintenance

The top cap can be brought to the ground by rotating the pipe on the trunnion. 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 (January 23, 2019)

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 have built and tested a trunnion to hold and rotate the pipe about the center of gravity. 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 corrugated 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've tested using double reflective insulation and found that this very efficient and cost-effective.

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
    • IN201817037964 filed with India patent office
    • In process with EU, Canada, Russia, Ukraine, Brazil, Mexico, and China patent offices

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