CelloFuel Portable Biomass Refinery

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

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Technology Overview

The CelloFuel technologies make ethanol close to where biomass is grown, eliminating the cost of transporting biomass to a more centralized location. CelloFuel modules also use a percentage of the ethanol that's produced to fuel the distillation process. Together, this eliminates the need for fossil fuels to produce ethanol.

The CelloFuel technologies can be scaled to industrial sizes, but are equally efficient at a farm-scale. Our initial product is a farm-scale product that is scaled up by replicating to hundreds of modules in parallel.

CelloFuel modules make ethanol from sugar-rich biomass such as sweet sorghum and sugar beet by infusing yeast into the biomass. A variant of CelloFuel modules makes hemicellulosic ethanol from softwood using dilute oxalic acid hydrolysis. In the future, CelloFuel modules will make hemicellulosic ethanol from agricultural wastes, such as corn stover and straw, using C5 yeast to make ethanol from the C5 sugars in hemicellulose.

CelloFuel modules infuse yeast into sugar-rich feedstocks, converting sugar-rich biomass into ethanol-rich biomass. Once ethanol-rich biomass is produced, a CelloFuel module uses a biomass distillation column to extract 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.

Feedstocks

Traditionally, sugar beets are grown in temperate climates, since cold winters help extend the sugar beet processing season. However, tropical sugar beets also grow well in tropical and sub-tropical climates. Sweet sorghum is normally grown in hot, dry climates and doesn't tolerate cold weather.

The two most important factors in choosing feedstocks are rainfall and whether there is a need to produce more than one crop per year. Sugarcane needs a lot of water, and needs either a lot of rainfall (i.e. Brazil) or a lot of irrigation (i.e. India). There are few areas in Africa that have enough rainfall to grow sugarcane. Sugarcane also can only produce one crop per year. However, both sweet sorghum and tropical sugar beets can be grown in areas with less rainfall, and can be grown on land that produces an energy crop half the year and a food crop the other half of the year. An effective crop rotation is sweet sorghum and soybeans, since soybeans fix nitrogen and replenish the nitrogen in the soil.

Sweet sorghum is a good feedstock for CelloFuel technologies because:

  • CelloFuel fermentation is more efficient than farm-scale crushing
  • Sweet sorgum produces both grain and sugars in the stalks
  • Ensiled sweet sorghum stalks are good for animal feed
  • Less water is needed than sugarcane or sugar beet
  • Less fertilizer is needed than sugarcane and sugar beet
  • Planting uses the same equipment as corn planting
  • Planting can be done without tilling land (no-till cultivation)
  • Harvesting can be done by hand or using the same equipment as sugarcane
  • Double-cropping with food crops such as soybeans and corn is feasible
Sugar beet is a good feedstock for CelloFuel technologies because:
  • CelloFuel fermentation is more efficient than hot water extraction
  • Ensiled sugar beets are good for animal feed
  • Less water is needed than sugarcane
  • Grows very well in tropical climates
  • Double-cropping with food crops is feasible
  • Sugar beet prices are dropping because of a surplus of sugar in the world

How is CelloFuel Different?

Using CelloFuel modules to produce ethanol eliminates expensive unit operations used by old-fashioned ethanol plants:

  • No need to transport biomass 20 to 100 km to a plant
  • No need to wash sugar beets, sugar cane or sweet sorghum
  • No need to crush sugar cane and sweet sorghum
  • No need to dispose of residuals (can plow back into field)
  • No need for fossil fuels
  • No need for limewater
  • No need for wastewater treatment (effluent is just water and yeast)
  • No need for antibiotics during fermentation
  • No need for biomass conveyors
  • No need for pumps
  • No need for lime kilns
  • No need for multi-effect evaporators
  • No need for distillation towers
  • No need for water chillers
  • No need for steam generators
  • No need for power generators

Process Details

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.
  • Sugar beet - impregnating with yeast using US Patent 9,499,839.
  • 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

Sweet sorghum must be harvested and fermented in a short time period (less than a month), so we have a technique for rapidly infusing the stalks with yeast, and then fermenting and distilling the ethanol over a longer period.

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 the ethanol produced by the CelloFuel modules, so this 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 ethanol 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
  • not using any kind of liquid pump

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 ethanol 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 ethanol 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
  • making all residues and waste water biodegradable - using only yeast and organic acids

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 12V 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. The rotation of the pipes is used for loading and unloading biomass, and also for mixing oxalic acid with biomass (softwood, stover and straw) and neutralizing with calcium hydroxide.

A CelloFuel module is designed for very low-cost manufacturing, and can be assembled and disassembled with hand tools - a screwdriver and a wrench. An inexpensive gasket is used to seal the end caps with the corrugated HDPE pipe. The end-caps, central girdle and trunnion require some metal 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.

No 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, and distributing these arrays of CelloFuel modules to where the biomass is grown. We expect this to scale up to the tens of thousands of CelloFuel modules, which is why we work hard to ensure low-cost manufacturing of each CelloFuel module.

Business Development

We're looking for manufacturers, distributors and customers, and our business plan allows for significant profits for each. We're not looking for investors, since we're fully funded. Our target markets for making ethanol from biomass are:

  • Sugarcane and sweet sorghum - India, Brazil, Mexico, China, Russia, Ukraine, USA, EU
  • Sugar beet - USA, EU, Russia, Ukraine, China
  • Tropical sugar beet - India and Brazil
  • Softwood wood chips - USA, EU, Canada, Russia, China
A byproduct of making ethanol from softwood wood chips is nanocrystalline cellulose.

Patent Status (May 13, 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 (April 16, 2019)

A 1/3 scale model of the CelloFuel module has been successfully built, and we're beginning construction of a full-size CelloFuel module that is 1 m in diameter and 6 m high (with a build cost less than $2,000). The 1/3 scale model 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, the top cap and the trunnion. CelloFuel Vertical Orientation CelloFuel Horizontal Orientation CelloFuel Top Cap 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 top cap has been assembled and installed, and the CelloFuel module holds a vacuum and does not leak when filled with water and rotated while filled with water under vacuum. This means it withstands 2.5 times the maximum loading. The evaporative cooling apparatus has been designed and is being tested. 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 1/3 scale CelloFuel module with top cap rotating around the trunnion.

Here is a video showing cutting the metal plate for the top cap with a plasma cutter.

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

CelloFuel Lab-Scale Apparatus

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