CelloFuel Portable Biomass Refinery

The CelloFuel Portable Biomass Refinery produces bioethanol from sugarcane, sweet sorghum, sugar beet and softwood wood chips. CelloFuel modules make bioethanol at a lower cost than existing technologies while at the same time producing bioethanol with a zero carbon footprint.

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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 - impregnating with yeast using US Patent 9,499,839 or 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 in air, then ensiling for up to a year
  • Distilling in corrugated HDPE pipes using US Patent 10,087,411, producing >90% Alcohol 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

Zero carbon footprint

CelloFuel modules have a zero carbon footprint. No fossil fuels are needed for transportation, because biomass isn't transported. Distillation heat is provided by bioethanol, which has a zero carbon footprint. Distillation cooling is provided by evaporative cooling, which also has a zero carbon footprint. Solar power is used to produce the electricity for the fan for evaporative cooling and for the control electronics, and has a zero carbon footprint.

Reduces CAPEX and OPEX

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 pressure vessels
  • not using a separate distillation column

Our goal is a CAPEX of less than $0.50 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 $1 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) of producing bioethanol by:

  • only fermenting C6 sugars - dry yeast only costs about $3 per ton of biomass
  • not using enzymes - dilute oxalic acid hydrolysis of softwood is much less expensive
  • not transporting biomass - by producing bioethanol near the source of the biomass
  • not separating sugars from biomass - by using yeast infusion instead of inefficient 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. About 10% of the hydrous ethanol can also be used as energy for distillation.

Energy for distillation heating

The CelloFuel modules need about 2 MJ heat per kg of ethanol distilled. Burning biomass is one way to produce heat for distillation, but most countries do not allow burning biomass in fields. CelloFuel modules burn ethanol to produce heat energy for distillation. Burning ethanol is very clean - it only produces CO2 and water vapor - and produces about 30 MJ of heat per kg ethanol burned. CelloFuel modules use less than 10% of the ethanol produced by distillation to power the distillation. This makes it possible for CelloFuel modules to operate in remote locations without burning biomass.

Energy for distillation cooling

The CelloFuel modules need about 2 MJ of cooling per kg of ethanol distilled. Water has a heat of evaporation of about 2.3 MJ/kg, and we're using evaporative cooling on the top cap to provide distillation cooling. This evaporative cooling works even with a relative humidity of 100% because air at 80 °C can hold much more water vapor than at 30 °C. This means a CelloFuel module will evaporate about a liter of water for every liter of ethanol produced. Evaporative cooling requires much less electricity for a fan than air cooling, so a CelloFuel module can do distillation in remote locations, using solar panels during the day which charge 12 V batteries for distillation at night.


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.

A CelloFuel module is designed for very low-cost manufacturing, and can be assembled and disassembled with hand tools - a screwdriver, a wrench and a bicycle pump. A bicycle tire is used to seal the end caps with the corrugated HDPE pipe. The end-caps, central girdle and trunnion require some plasma cutting, metal rolling and a bit of welding to manufacture, everything else can be made with a metal saw and a drill. The trunnion does not need a bearing. When disassembled, multiple CelloFuel modules can be efficiently transported in 20 ft. shipping containers.

The top and bottom of the HDPE pipe are joined with steel plates. When using oxalic acid with softwood, these are made from type 444 stainless steel, which is resistant to corrosion by oxalic acid (as is HDPE). The top cap uses water for evaporative cooling for a dephlegmator and condensor. The top cap has a lid that can be lifted off the HDPE pipe for biomass loading and unloading. An ethanol burner, like a chafing dish, is used to apply heat to the bottom cap for distillation.

Multiple HDPE pipes are mounted in rows so that they can be loaded and unloaded efficiently.

Safety and Environment

Burning ethanol for distillation energy is very safe. Restaurants commonly use chafing dishes containing ethanol, and these emit no toxic or smelly fumes. When ethanol is burned in a chafing dish, there's no risk of explosion and the rate of burning can be easily controlled.

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. Biomass that has been infused with oxalic acid and neutralized with calcium hydroxide is also biodegradable.

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 in arrays.

Patent Status (March 19, 2019)

There are three families of CelloFuel patents for making ethanol that have been granted in the US and around the world, including the US, EU, Canada, Russia, China, Mexico and Brazil.

There is one family of CelloFuel patents for making nanocellulose from softwood that has been granted in the US and around the world, including the US, EU, Canada, Russia and China (all countries with a significant amount of softwood).

Project Status (March 19, 2019)

A scale model of the CelloFuel module is being built, and is scalable to 1 m in diameter and 6 m high. It has a volume of 1/2 m3, where the full-size CelloFuel module is 5 m3. Here are some pictures of vertical orientation, horizontal orientation and a closeup of the trunnion. CelloFuel Vertical Orientation CelloFuel Horizontal Orientation CelloFuel Trunnion

This is for testing rotation, biomass loading (tilted at 45 degrees), unloading (tilted at 135 degrees), and mixing with yeast and other reagents such as oxalic acid (turning upside down and back). We've tested with 1800 W of heat using double reflective insulation and found that this is very efficient and cost-effective.

A vacuum test of 12 kPa with this CelloFuel module was successful, with no leaks. The next step is a hinged door on the top cap (for loading and unloading biomass). A plasma cutter is on order so this can be manufactured in our lab. Once this is done, we need to test distillation by insulating the pipe, installing an induction heater under the bottom cap and installing evaporative cooling on the top cap (dephlegmator and ethanol condensor). We also need to design and build an ethanol heater for the bottom cap.

Here is a video of the CelloFuel module rotating around the trunnion.

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

CelloFuel Lab-Scale Apparatus

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