Cash from trash with Biofuel

From biogas made from slaughterhouse waste and alcohol seized by customs officials in Sweden to biodiesel made from restaurants’ used cooking oil in the United States to bioethanol made from agricultural waste in China the fuel-from-waste industry is emerging as a way to help cut reliance on fossil fuels.

“All biomass waste can be used for energy purposes,” says Tomas Kåberger, director general of the Swedish Energy Agency and a former bioenergy industry executive and professor at the leading environmental institute at Lund University in Sweden. “The total global potential of residues from forestry and agriculture and other sources is between a quarter and a half of total commercial energy use, but sometimes the cost of utilization is too high. However, as oil prices have escalated the economic potential has increased significantly – and more quickly than people have realized.”

Mankind generates an estimated 4 trillion tonnes of waste a year, so it makes an attractive energy source. And it has the obvious advantage of reducing fossil fuels use and subsequently greenhouse gas emissions. In the case of biogas and second-generation ethanol, there is a further benefit: When organic waste decomposes it creates methane, which is 20 times more forceful as a greenhouse gas than CO2. If you use it to make second-generation ethanol instead, that methane is never released, and if you make biogas it is captured. “Reducing emissions of methane may be just as important as substituting fossil fuels in the engine,” says Kåberger.

But for most businesses today, economic considerations still have the upper hand, and here biofuels from waste still make sense. “You avoid traditional waste management costs and produce a valuable product instead,” says Kåberger. “There are opportunities that are very profitable today that were not profitable when these resources were evaluated five or 10 years ago, when the oil price was lower. And there are market opportunities that are still to be discovered.”

Today the world leaders in biofuel development and use are Brazil, the United States, France, Sweden and Germany, although China is becoming a major player thanks to the likes of China Clean Energy, which is increasing its production of biodiesel made from recycled cooking oil and other waste food oils by 100,000 tonnes per year. The US military has taken a leading role in the fuel-from-waste industry, with projects ongoing to make jet fuel out of wood pulp and agricultural waste.

The business potential of biofuels from waste can be seen in the fact that major corporations – including oil giants such as Shell, BP and Chevron – are also getting involved. British Airways is investing in a plant that will turn 500,000 tonnes of organic waste into 73 million litres of jet fuel per year, while Alfa Laval, which is a leading supplier of equipment to biofuel producers, has acquired Ageratec, a much-talked-about manufacturer of biodiesel processors.

“Some small start-ups are strong on the technology side but weak on marketing and scaling up production, and they benefit from joining large established companies,” says Kåberger. Gert Ternström, marketing manager biofuels at Alfa Laval, says that technology development has helped create a situation in which biofuels made from waste can compete with fossils fuels on increasingly even terms.

“If you look at making diesel from animal fat, it is a more difficult process than making it from crude vegetable oil, but the cost of production has been reduced significantly,” he says. “We are now in a more mature phase of the biofuels business where an infrastructure has been built up. So making fuel from waste is a no-brainer when you look at it today, although it was just a few years ago when you didn’t have the incentives to run this business.”

Kåberger expects the fuel-from-waste market to grow rapidly in the short term. “As they [fuel-from-waste businesses] are growing from a very small scale they will not get major market share in the short term because the fossil fuel market is enormous,” he says. “But in the longer term they will become a significant part of the automotive fuel market because oil resources are limited and biofuels are not.”

The main technical breakthroughs needed for wider implementation of biofuels from waste have already been made. “There are a lot of opportunities for marginal improvements in yields and marginal reductions in cost, but I don’t think we can identify one key solution that will make it more competitive,” says Kåberger. The political constraints to wider implementation of biofuels made from waste are minor. For instance, the European Union’s biofuels directive commits member states to 10 percent biofuels in traffic fuel by 2020.

“I think the most important constraint is that too few people understand the technological and economic opportunities,” says Kåberger. “Waste has always been waste, and few have the imagination to realize that it can be industrially converted into automotive fuels at reasonably low cost. By doing so, you reduce the economic and environmental costs of handling it and at the same time create a new revenue stream.”

Power to the people – from slurry

Lemvig Biogas, built in 1992, is Denmark’s largest biogas plant, producing about 8.5 million cubic metres of biogas a year to generate electricity and heat. The biogas is made from slurry from about 75 local farms, which are part owners of the plant, as well as waste and residual products from industrial production, including slaughterhouse and brewery waste, contaminated food and waste from the pharmaceuticals industry.

From the biogas produced, more than 21 million kWh electricity is generated per year and sold into the local power grid. The surplus heat from the gas engine cooling system exceeds 18.3 million kWh per year and is distributed to the users of the Lemvig central heating plant (about 1,000 households).

Biogas is produced by the biological breakdown of organic matter in the absence of oxygen. The Lemvig plant employs a method called “thermophilic fermentation,” which uses bacteria that have to be kept at temperatures as close to 52.5°C as possible. Generating this heat would normally require about 9,000 MWh of energy, corresponding to 16 percent of the facility’s total power output. By using four Alfa Laval spiral heat exchangers, the Lemvig plant needs only 6,000 MWh of energy to maintain the temperature. The rest is retrieved by heat transfer using digested sludge as the hot media. The heat exchangers draw heat from the digested manure flows that cool from 52°C to 29°C to preheat the incoming undigested organic waste from 15°C to 44°C.

The solution brings improvements in revenue for the plant and its owners. “If we had to use the heat we produce to maintain the required operating temperature, we’d have much less to sell,” explains Lemvig Managing Director Lars Kristensen. “Alfa Laval’s heat exchangers have ensured us maximum efficiency.”

Ultimate green fuel is locally produced

Finnish energy company St1 is making bioethanol for transport use. The fuel (basically alcohol) is made from waste and industrial side streams with the company’s Etanolix method. Etanolix has an extremely low carbon footprint: It uses waste as feedstock; it uses renewable energy in production; and it applies new energy-efficient processes and technologies. It also has minimal transport needs, as it is made in small production units that are built close to the source of the feedstock. In addition, by-products from the process such as fertilizers, animal feed and solid biofuel are utilized locally.

St1 currently has six waste-to-ethanol units producing 5,000 cubic metres of fuel per year from about 45,000 tonnes of waste. The Etanolix process was designed specifically to convert food industry wastes and side streams into ethanol. It uses biowaste from food processing plants as well as food industry by-products that contain sugar, starch or low concentrations of ethanol. This includes potato processing waste, bakery waste and side streams, dairy industry waste and side streams, and brewery waste.

The production process involves the microbial fermentation of the sugars in the raw material. From the production units the 85 percent bioethanol is transferred to a separate dehydration unit for dewatering, after which the 99.8 percent bioethanol is ready to be blended with petrol and distributed to service stations. St1 uses Alfa Laval compact plate heat exchangers in its ethanol rectification process. The heat exchangers are used for heat recovery, boiling and condensation.

St1 also uses some raw materials, such as food industry waste, that require spiral heat exchangers that can heat sludge or fibrous media better than other technologies. St1 is developing new methods to utilize an even wider selection of wastes and industrial side streams. Its next-generation plants, which are currently under development, will run on commercial packaging and straw, among other materials.

Fuel from fat boosts engine performance

In the northern German town of Malchin, Saria Group subsidiary ecoMotion has been producing second-generation biodiesel from animal by-products since 2001. The raw material for the plant includes animal fat from a nearby rendering factory as well as used cooking oil.

The Malchin plant is one of three owned and operated by the Saria Group, with a total capacity of 212,000 tonnes of biodiesel per year. Their output has the potential to save nearly 400,000 tonnes of CO₂ per year – equivalent to the emissions of 170,000 households or about the same number of cars. During the process, the raw material and a methanol catalyst mixture are pumped to a unit where they undergo a process called transesterification. The biodiesel is created by an alkali catalysed reaction between fats or fatty acids and methanol.

The facility, which produces 12,000 tonnes of high-quality biodiesel per year, uses the Alfa Laval Centrifine process to purify fats from slaughterhouse by-products until they contain no more than 0.15 percent impurities by weight. After cleaning with a decanter centrifuge and disc stack centrifuge, the product can be used to produce steam or biodiesel. The fuel itself is 97 percent pure, with a low sulphur content. By-products of the process include solid fertilizer and glycerine, which in turn can be split into free fatty acids, crude glycerine and solids. Free fatty acids are reused and converted into more biodiesel, while crude glycerine and solids are sold for further processing.

Besides the environmental benefits, recent studies have shown that biodiesel produced from 100 percent animal fat – also called animal fat methyl ester, or AFME – contributes to better overall engine performance. Compared with conventional fossil diesel, this type of biodiesel improves engine efficiency, reduces exhaust emissions and lowers engine noise levels.

For second-generation biodiesel made from animal fats, particulate matter and CO₂ concentrations are even lower than for rapeseed oil methyl ester (RME, or first-generation biodiesel made from rapeseed oil). AFME also has better lubricating properties than RME. Fuel from the Malchin plant has been used in more than 1,000 trucks since production started in 2001. Tests have proved the benefits with regard to emissions with no increase in technical faults.