Production

General

Bio refinery

Processes

Processes

Weak and Strong acids and Enzyme process
In the process of weak acids the cellulose is split into fermentable types of sugar in two stages with the help of different acids such as sulphuric acid and sulphur dioxide. The raw material containing cellulose is usually from wood shavings or wood filings, but recycled fibre that does not contain plastic can also be used. Wood consists of three important elements i.e. cellulose, semi cellulose and lignin. In the first phase the semi cellulose is split and the cellulose in the second phase. The temperature in the first phase is around 190 degrees and in the second phase it is 225 degrees. The acid is diluted and thus high temperatures are required for the splitting process. The splitting takes place very rapidly at high temperatures, but there is a risk that the sugar might continue to break up even further, thus making it impossible for fermentation.
In the strong acid process, concentrated acid is used at a low temperature that results in less by-products and greater value. The problem is to separate sugar and acid, such that the recycled acid has minimal effect on the environment.
The splitting in the enzyme process occurs at an increased room temperature. The enzymes take along time to split the cellulose, so they lie in large tanks maybe even for a day.

Carbon dioxide and ethanol
The sugar solution is washed out from the residue after each reaction occurs and is pumped into the fermenting tank. After this, baking yeast is added and this adjusts itself to the food and the environment that it lives in. During fermentation the quantity of carbon dioxide is equivalent to that of ethanol. Carbon dioxide is collected and purified for using in beverages and fire extinguishers. After fermentation, ethanol is distilled from the sugar solution. 95% of the sugar solution becomes purified ethanol. The remaining solution is purified with other bacteria, and is converted into methane gas that is also called biogas. They can also be dehydrated by evaporation and used for burning in furnaces of power heating plants.

High energy content
The residue after the second reaction is lignin, which is the third important element in wood.
The lignin is dried and made into pellets after the washing process. This fuel, which is easy to handle has a 30% higher energy content than bio pellets. The other alternative would be to use the damp lignin directly in the furnaces of power heating plants. From 100 kg of dry wood 20-25 kg of ethanol, 20 kg of carbon dioxide, 45 kg of lignin pellets is obtained. The remaining 10-15 kg is converted into biogas, or used in furnaces for heating purposes during distillation processes.

Advantages of enzymes
The weak acid process is similar to that of the enzyme process, where the splitting of the cellulose takes place with enzymes after one or two stages. The second stage of the weak acid reaction can be replaced with an enzyme reaction when the technique is fully developed. Lab tests show that the result is much greater in the enzyme process, since it does not break down the sugar as seen in the acid hydrolysis.

Pilot project in Domsjö
The project technique is not fully developed and tested, so a research and pilot facility has been established in Sekab's premises at Domsjö factory in Örnsköldsvik. The research facility will be a fully furnished factory, but will not produce ethanol for selling purposes. It will have a production capacity of 200 cubic metres of ethanol per year. It is associated with the University in Örnsköldsvik, and is also going to have a research and development centre for process techniques in co-operation with Lunds University, Chalmers and others.

Production Facility
The investment required for a production plant with a capacity to produce 50,000 cubic metres of cellulose-based ethanol per year is approximately SEK 1 billion. The plant will be able to provide employment for 45-60 people, transportation and raw material procurement will need 40-80 people depending on the kind of raw material that would be used and how the bio energy reserve will be built. Preliminary studies for production plants with different bio energy reserves have been carried out in various parts of the country.