CelloFuel Portable Biomass Refinery

We develop the CelloFuel Portable Biomass Refinery, for producing low-carbon bioethanol from sugar beet, sugarcane, sweet sorghum, softwood wood chips, stover, cassava, Jerusalem artichoke, and potatoes. Our goal is to make bioethanol at a lower cost than existing technogies 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. Our goal is to also make rare sugars from softwood and nanocellulose from stover.

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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 sugar beets, 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 other feedstocks, 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 biomass into vertical HDPE pipes from the top
    • Sugar beet - commercial auger bucket
    • Sugarcane/sweet sorghum - billets in front-loader bucket with funnel
    • Softwood forestry residues - commercial wood chippers and auger bucket
    • Stover - commercial auger bucket
    • Cassava/Jerusalem artichoke/potatoes - auger bucket
  • Softwood/stover - dilute oxalic acid hydrolysis of hemicellulose at 95 C for 48 hours, neutralization with calcium hydroxide
  • Cassava/potatoes - dilute oxalic acid hydrolysis of starch at 95 C for 4 hours, neutralization with calcium hydroxide
  • Jerusalem artichoke - dilute oxalic acid hydrolysis of inulin at 95 C for 4 hours, neutralization with calcium hydroxide
  • Impregnating biomass with yeast using US Patent 9,499,839
    • Sugar beet/sugarcane/sweet sorghum - normal yeast (Saccharomyces cerevisiae)
    • Softwood/stover - C5/C6 fermenting yeast (i.e. XyloFerm)
    • Cassava/Jerusalem artichoke/potatoes - normal yeast (Saccharomyces cerevisiae)
  • Solid-state fermentation of sugars to ethanol with periodic vacuum cooling
  • Distilling in HDPE pipes under vacuum at 50 C using US Patent 10,087,411
  • Emptying residual biomass from vertical HDPE pipes from the bottom.
  • 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.


Produces rare sugars from softwood

Our patented pressure cycling technologies (US Patent 9,194,012) are useful for extracting rare sugars from softwood (mannose, arabinogalactan and galactoglucomannan). These sell for more than $10/kg, making these a more valuable product than ethanol.


Produces nanocellulose from softwood and stover

The residual stover after dilute oxalic acid hydrolysis contains nanocrystalline cellulose that has been carboxylated, and thus degrades at a much higher temperature than nanocellulose produced with sulphuric acid. We are working on extracting this high-temperature nanocellulose from the residual stover for use in drilling mud. See Schlumberger and Halliburton patent applications for more info about this application.

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, sufficiently thick to withstand a vacuum inside the tube. Suspended under the top cap is a coil of PEX pipe which circulates water for the dephlegmator and condenser. 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. The bottom cap normally holds the weight of the HDPE pipe when full, and can be lowered with a jack, turning it into a chute which conveys the residual biomass out of the HDPE pipe. An induction heater or steam heater is used to apply heat to the bottom cap. HDPE, fusion bonded epoxy and PEX pipe 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 and/or vacuum. If there's an unexpected steam pressure build-up, the top cap raises up and releases steam. When using the HDPE pipe under vacuum, a failure simply leads to implosion, which is quite safe (and unlikely).

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 winched to the ground for maintenance. The various connections to the HDPE pipe are easily accessible.

If a vandal shoots bullets into an HDPE pipe, the bullet holes are often self-sealing. In the event of a very determined vandal, the worst case is that a hole in the HDPE wall causes a leak or loss of vacuum. This can easily be repaired in the field by plastic welding.

Reduces scale-up risk

A CelloFuel module is a single vertical HDPE pipe held up by a scaffold. Scaling up to larger scales involves simply replicating the HDPE pipes and scaffolding in arrays.

Portability

Mounting and dismounting the HDPE pipe and top cap is done with a winch at the top of scaffolding. The HDPE pipes, winches and scaffolding are transported in standard 20 ft. shipping containers. An air-cooled ethanol condenser, vacuum pump, IBC containers for chemicals, and an IBC container for ethanol are located in a 20 ft. shipping container.

Project Status (October 18, 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. The HDPE pipes have been tested for vacuum with steel plate end-caps.

We are currently constructing a mechanical mockup of the pilot-scale reactor that we will use to test loading and unloading biomass. The scaffold has been received, and we will test biomass loading/unloading with this apparatus and a front-loader. Note that the scaffold only has to hold the weight of the empty HDPE pipe and the floor jack holds up the bottom cap, which holds the weight of the HDPE pipe when full of biomass. This is scalable to HDPE pipes up to 1 m in diameter and 6 m high.

Here is a video of how the scaffold, pipe and the unloading chute work. This was just a preliminary mock-up - the final design of the hinge and chute are different.

Patent Status (October 16, 2018)

There are four 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.

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