Thermocatalytic biorefining of biomass via the Biofine process
16 May 2013
Author: Dr Stephen Fitzpatrick PhD, founder and chief executive of Biofine Technology LLC
The Biofine process is a high temperature, dilute acid-catalysed rapid hydrolysis of lignocellulosic biomass. The process cost-effectively refines biomass into four principal products that can be separated and purified for sale: levulinic acid, a versatile platform chemical; formic acid and furfural, which are commodity chemicals; and a carbonaceous ‘bio-char’ consisting of over 60% carbon that can be burned or gasified to produce steam and electric power.
The process is carried out in a novel, continuous two-stage thermocatalytic reactor system that enhances the yield of the major product, levulinic acid, to over 70% of theoretical, making the process commercially viable. Unlike biological processes that can take several days, the main biomass conversion process is very fast, being complete in under twenty minutes. Because of its non-biological, thermocatalytic nature, the process is flexible enough to utilise a wide range of lignocelluloses such as forest residues, waste paper, paper sludge or straw and other carbohydrate materials such as starch and sugars.
The process consists of five main continuous processing steps to convert raw lignocellulose to levulinic acid. The raw feedstock is chipped and fed to a pre-treatment to remove hemicellulose. The high-cellulose residue is then slurried with dilute acid and pumped into the first-stage plug flow reactor, where the temperature is raised to 210 degrees Celcius. The residence time in the first reactor is 15 seconds.
The first-stage reactor breaks down the cellulose into a mixture of sugars and hydroxymethylfurfural. This mixture then flashes into a second stage, completely mixed reactor where the sugars are converted to levulinic and formic acids in a residence time of fifteen minutes at below 200 degrees C. The insoluble char byproduct produced in the reaction is separated and levulinic acid is then extracted and purified from the clarified hydrolysate. Formic acid is extracted from the flash vapours and the pentose fraction of the pre-extracted hemicellulose is converted to furfural by acid-catalysed dehydration.
Levulinic acid is known, at present, as a specialty chemical with limited markets in food, chemicals and pharmaceuticals. It is, however, an extremely versatile platform chemical that can be converted into a wide range of products. Levulinic acid has been identified by the US Department of Energy as one of the key chemicals in the utilisation of renewable cellulosic resources to displace chemicals made from crude oil or coal. The Biofine process has the potential to contribute significantly to US Department of Energy goals and allow biomass to displace crude oil as a primary source of fuels and chemicals.
Of particular commercial interest is the production of methyl and ethyl levulinate esters, versatile fuel products that can be mixed with biodiesel to form a low carbon footprint blend-stock for heating oil and commercial diesel. It is manufactured by the reaction of levulinic acid with either methanol or ethanol. The development of a renewable heating oil or transportation fuel blending component that can be blended with oil-seed-derived biodiesel, economically produced and used in a local environment should be of great commercial and social interest.
TRANSPORTATION FUEL MARKETS
Test work on levulinate esters in heating oil blends with biodiesel is currently being carried out in the USA at Brookhaven National Laboratory, NY. The market for heating oil in the US is seven billion gallons. Blending levulinate esters at 5% would require the output from ten large-scale Biofine plants utilising 1,000 dry tons per day of wood or other biomass. Transportation fuel markets in the US for gasoline and diesel are 140 billion and over 50 billion gallons respectively and represent a huge, longer-term potential use of the technology.
Levulinic acid can also be converted to hydrocarbons chemically, e.g. via aldol condensation and hydrogenation allowing the promise of renewable jet fuel to be produced directly from cellulose. Work on a thermal conversion process is currently under way at the university of Maine at Orono Chemical Engineering Department to optimise a direct non-catalytic thermal process that converts the output from the Biofine process into an energy-dense liquid hydrocarbon fuel with an energy content of around 42 MJ/Kg.
Green chemical derivatives of levulinic acid include monomers, pesticides and general chemicals. Chemical products include diphenolic acid, a displacement for toxic bisphenol A in epoxy resins and polycarbonates, levulinic ketal, a displacement for toxic phthalates widely used as components of plastics used in consumer products and deltaaminolevulinic acid (DALA), the natural precursor for chlorophylls and other tetrapyrroles that shows promise as a natural selective pesticide.
Formic acid is a commodity chemical with a present-day market of over 500,000 metric tons. It is used in animal-feed ensiling, leather tanning and as an agricultural antibiotic. In response to a reduction in price, its present market can be expanded greatly. Formic acid can be used as a hydrogen carrier for fuel cells, as it spontaneously evolves hydrogen in contact with certain metal catalysts. It is has the equivalent fuel value of hydrogen at 350 atmospheres. The ammonium salt, ammonium formate has advantages over urea as a means of scrubbing nitrogen oxides from boiler flue gas and vehicle exhausts.
Furfural is a commodity chemical with a present-day market of around 300,000 metric tons. It is used for the manufacture of foundry resins and in the production of lubricating oils. It can also be used as the starting material in production of other commodity chemicals such as furfuryl alcohol, butanediol and tetrahydrofuran. Furfural can be sold into the market or it can also be converted directly to levulinic acid, thus greatly increasing the yield of the main product of the process.
The carbonaceous bio-char consists of around 60% carbon. It is a mixture of carbon residue from the acid hydrolysis reaction and lignin in the original feedstock. It is produced as a finely divided, hydrophobic black powder that lends itself very well to dewatering and burning to provide all the energy the process requires. It has an energy content of 25 MJ/Kg. Alternatively, it can be used as a non-biodegradable soil amender and has potential as a feedstock for carbon fiber or activated carbon production.
A semi-commercial scale plant is now operational in the USA in Old Town, Maine that can process up to two tons per day of a variety of feedstock. It is a fully computer controlled plant that can operate continuously for testing of feedstock and process optimisation.
GREENHOUSE GAS MITIGATION
The process is extremely attractive as part of a greenhouse gas mitigation strategy. It was recently assessed to have a greenhouse gas (GHG) life-cycle saving of over 90% better than gasoline or diesel fuel and 40% better than soy-based biodiesel by independent assessors using the USDOE-developed GREET methodology. In addition, the Biofine process affords the ability to produce formic acid from a renewable source, eliminating the use of fuel oil or butane in the conventional formic acid process. This gives an even higher greenhouse gas saving.
The process also has potential to stimulate the rural economy, allowing farmers to produce crops such as miscanthus Spp that can be used for fuel and chemicals production. This could keep the domestic farm economy buoyant by allowing farmers an alternative or additional source of revenue during poor market periods.
The Biofine process can be advantageously installed into existing operations such as pulp and paper mills, power plants and municipal solid waste recycling facilities, taking advantage of underutilised established locations that have operating permits. In this way, older rust-belt facilities can gradually be converted to more modern renewable fuels and chemicals uses with widespread social benefit.
At large scale, the process is projected to allow profitable production of heating oil blend stock from wood or agricultural residues for under two dollars per gallon and levulinic acid as a chemical feedstock for around $1,000 per ton.
In summary, the Biofine process has potential to touch many aspects of society in establishing sustainability from all perspectives, social, economic and environmental. In addition, for Ireland, its widespread introduction will benefit the rural economy, create jobs, reduce the need for crude oil imports, provide cleaner burning fuels and help the country meet its goals for reduction of greenhouse gas emissions.
Dr Stephen Fitzpatrick is a chemical engineer with over 30 years’ industrial operational and consulting experience. He is inventor of the Biofine technology and has been actively involved with its commercial development for more than 20 years. Dr Fitzpatrick is also co-founder and president of DPS Biometics LLC, the US-based subsidiary of DPS Engineering (Dublin), an engineering and consulting company specializing in facilities design for biopharmaceutical processing, electronics and biomass conversion. He is an internationally recognised expert in technology development and biomass-derived renewable fuels and chemicals.
Dr Fitzpatrick’s early industrial operating experience was in research and development, pharmaceuticals, general chemicals and oil refining. He then moved from the UK to the USA working in technology development.
He holds bachelors, masters and doctoral degrees in chemical engineering from the University of Manchester and is a chartered engineer in the UK. His awards and honors include the 1972 Dista prize for biochemical engineering (University of Manchester) and the 1999 Presidential Green Chemistry Challenge Award for his development of the Biofine process.http://www.engineersjournal.ie/2013/05/16/thermocatalytic-biorefining-of-biomass-via-the-biofine-process/http://www.engineersjournal.ie/wp-content/uploads/2013/05/Biofuel1-1024x683.jpghttp://www.engineersjournal.ie/wp-content/uploads/2013/05/Biofuel1-300x300.jpgBiobiomass,climate change,energy