31
October 2011
A chemical process can that can transform a wide range of waste streams into a hydrocarbon fuel oil has been developed by researchers at the University of Maine (UMaine).
According to the university, the new process is based on a mixed-carboxylate platform, developed by M. Clayton Wheeler, a UMaine associate professor of chemical and biological engineering, alongside undergraduate students in his lab.
The researchers also claims that the new fuel has been determined to have a number of properties that make it better suited to serve as a drop-in fuel than many hydrocarbon fuels currently being developed, and even those currently on the market.
The feedstock for the process can include forest residues, along with other materials such as municipal solid waste, grasses, and construction and demolition wastes.
According to Wheeler, the process by which the oil is created, known as thermal deoxygenation or TDO, is relatively simple and will work on the cellulose found in wood or other substances that contain cellulose or carbohydrates.
The process starts with the conversion of cellulose into organic acids. The acids are combined with calcium hydroxide to form a calcium salt. That salt is heated to 450 degrees Celsius in a reactor, which constantly stirs the salt. This produces a reaction resulting in a dark amber coloured oil.
The reaction removes nearly all of the oxygen from the oil, which the researchers say is a key step that distinguishes TDO from other biofuel processes.
Oxygen is removed as both carbon dioxide and water, 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," explains Wheeler. "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."
Oxygen can be removed by using hydrogen, which is expensive and decreases the energy efficiency of your process. However, if there's a way to remove the oxygen from the biomass chemically, then it will be significantly densified, Wheeler explains.
"Our oil has less than 1% oxygenates. No one else has done anything like this," he adds.
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 produce a batch of the fuel.
UMaine say that the use of municipal solid waste illustrates another important point about the potential of the fuel - it does not require an uncontaminated cellulose source, which makes the TDO process and resulting oil even more attractive. Many other pathways to hydrocarbons require purified feedstocks or intermediates, which adds more complexity and cost to those processes.
"You don't need pure wood or pure cellulose," says Wheeler. "Anytime you can use something without having to separate it, your costs go down."
Wheeler and his team say that they already have the ability to produce several litres of the fuel per month in the laboratory, and claim that the process can be scaled up using equipment and chemicals commonly found in facilities such as some pulp mills.
The university says that in an early round of analysis the oil produced by the process was found to have boiling points that encompass those of jet fuel, diesel, and gasoline.
Further refinement to meet emissions standards would be needed in order to use the UMaine oil in vehicles that drive on public ways, but Wheeler believes the oil can be refined as simply as any other current oil at a standard refinery.
A chemical process can that can transform a wide range of waste streams into a hydrocarbon fuel oil has been developed by researchers at the University of Maine (UMaine).
According to the university, the new process is based on a mixed-carboxylate platform, developed by M. Clayton Wheeler, a UMaine associate professor of chemical and biological engineering, alongside undergraduate students in his lab.
The researchers also claims that the new fuel has been determined to have a number of properties that make it better suited to serve as a drop-in fuel than many hydrocarbon fuels currently being developed, and even those currently on the market.
The feedstock for the process can include forest residues, along with other materials such as municipal solid waste, grasses, and construction and demolition wastes.
According to Wheeler, the process by which the oil is created, known as thermal deoxygenation or TDO, is relatively simple and will work on the cellulose found in wood or other substances that contain cellulose or carbohydrates.
The process starts with the conversion of cellulose into organic acids. The acids are combined with calcium hydroxide to form a calcium salt. That salt is heated to 450 degrees Celsius in a reactor, which constantly stirs the salt. This produces a reaction resulting in a dark amber coloured oil.
The reaction removes nearly all of the oxygen from the oil, which the researchers say is a key step that distinguishes TDO from other biofuel processes.
Oxygen is removed as both carbon dioxide and water, 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," explains Wheeler. "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."
Oxygen can be removed by using hydrogen, which is expensive and decreases the energy efficiency of your process. However, if there's a way to remove the oxygen from the biomass chemically, then it will be significantly densified, Wheeler explains.
"Our oil has less than 1% oxygenates. No one else has done anything like this," he adds.
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 produce a batch of the fuel.
UMaine say that the use of municipal solid waste illustrates another important point about the potential of the fuel - it does not require an uncontaminated cellulose source, which makes the TDO process and resulting oil even more attractive. Many other pathways to hydrocarbons require purified feedstocks or intermediates, which adds more complexity and cost to those processes.
"You don't need pure wood or pure cellulose," says Wheeler. "Anytime you can use something without having to separate it, your costs go down."
Wheeler and his team say that they already have the ability to produce several litres of the fuel per month in the laboratory, and claim that the process can be scaled up using equipment and chemicals commonly found in facilities such as some pulp mills.
The university says that in an early round of analysis the oil produced by the process was found to have boiling points that encompass those of jet fuel, diesel, and gasoline.
Further refinement to meet emissions standards would be needed in order to use the UMaine oil in vehicles that drive on public ways, but Wheeler believes the oil can be refined as simply as any other current oil at a standard refinery.
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