New University of Maine Thermal Deoxygenation Process Biocrude

A University of Maine chemical engineer and his research team have developed a new process—thermal deoxygenation (TDO)—to transform biomass, including forest residues, municipal solid waste, grasses, and construction wastes, into a hydrocarbon fuel oil. The process requires no catalysts or hydrogen, and is “a spin on chemistry used to make acetone back in the 1800s”, said M. Clayton Wheeler, a UMaine associate professor of chemical and biological engineering. _GCC

The biocrude can be used as a substitute for heating oil, but for use as transportation fuel it would require further processing. Here are more details on the process:

The TDO process starts with the conversion of cellulose to organic acids. The acids are then combined with calcium hydroxide to form a calcium salt. That salt is heated to 450 °C (842 °F) in a reactor, which constantly stirs the salt. This produces a reaction resulting in a dark amber-colored oil.

The reaction removes nearly all of the oxygen from the oil as both carbon dioxide and water, and without the need for any outside source of hydrogen to remove the oxygen. Therefore, most of the energy in the original cellulose source is contained in the new oil.

Biomass has a lot of oxygen in it. All of that oxygen is dead weight and doesn’t provide any energy when you go to use that as a fuel. If you’re going to make a hydrocarbon fuel, one of the things you have to do is remove oxygen from biomass. You can do it by using hydrogen, which is expensive and also decreases the energy efficiency of your process. So if there’s a way to remove the oxygen from the biomass chemically, then you’ve densified it significantly. Our oil has less than 1 percent oxygenates. No one else has done anything like this.

—Clay Wheeler

The TDO process does not require an uncontaminated cellulose source; researchers in Wheeler’s lab at UMaine recently used unpurified, mixed carboxylates which were produced from grocery store waste such as banana peels, cardboard boxes and shelving to successfully make a batch of the fuel. _GCC

It is one thing to make biocrude from biomass. But to do it economically, at low cost, is another story. The economic viability of the U. Maine process above apparently depends upon being able to obtain waste biomass feedstock cheaply.

Here is the bottom line: Conversion of biomass to liquid fuels (BTL) must compete with gas-to-liquids (GTL) and coal-to-liquids (CTL), as well as conventional petrofuels, in the marketplace. For areas which are "biomass rich" and "gas and coal poor," BTL may have an advantage over GTL and CTL, as long as the feedstock can be obtained cheaply. If the new U. Maine process allows for cheap decentralised TDO processing close to the source of the biomass feedstock, it could shift the balance of costs in the favour of BTL -- for specific locations.

See earlier report on this line of research, which specifically mentions a sulfuric acid bath as one method for converting cellulose to organic sugars.