PROJECT DESCRIPTION
BACKGROUND
Rice growers commonly deal with rice-straw waste by burning it, emitting carbon dioxide into the atmosphere. The production of rice in the European Union in 2012 amounted to 3.05 million tonnes. The amount of straw generated is 0.8 tonnes per tonne of rice produced. Thus, 3.05 million tonnes of rice equates to 2.4 million tones of this waste, resulting in 4.1 million tonnes of CO2 emitted during the burning process.
Alternatives to rice-straw burning have been researched but none has so far resulted in a low-cost, sustainable, practical solution. Any alternative use of the rice straw must be economically viable for rice growers.
OBJECTIVES
The LIFE WALEVA project aimed to demonstrate how the environmental damage from the burning of rice straw can be eliminated, and the waste can be deployed as raw material with added value by the introduction of a new value chain which ends in the production of LEVA (levulinic acid), a chemical monomer that is in demand because of its uses in a multitude of industrial sectors, including pharmaceuticals, biofuels, general chemistry, polymers and food.
The chemical process, developed in the laboratory by the beneficiary in 2012, would be demonstrated in a pre-industrial plant which will treat 0.5 tonnes/month of rice straw and produce 75-100 kg/month of LEVA. This technology would also be able to utilise other waste streams generated during the process: a stream rich in xylose (XYL) and a solid (bio-charcoal) that will be used to provide energy to the process, making it more energy efficient.
RESULTS
The LIFE WALEWA project demonstrated an innovative way to valorise rice straw through the chemical transformation of its cellulose fraction into levulinic acid (LEVA), which has a range of industrial applications. It created a pilot plant that was able to treat one tonne of residue per month. The plant, which comprised a mechanical pre-treatment unit, a chemical acid pre-treatment unit, an acid hydrolysis unit and a purification unit, operated for 1 080 hours over nine weeks, functioning continuously for five days a week. During this period, it produced 180 kg of LEVA.
Although the efficiency of purification process was lower than that achieved in the laboratory, the pilot plant produced a significant 10.4% yield of LEVA with a purity of 89.7%. The process parameters were adjusted to optimise the energy consumption and thus increase the cost effectiveness of the project’s approach. Based on the pilot results, the project team calculated that an industrial plant treating 624 000 tonnes of rice straw annually could turn a profit from the sale of the LEVA yield and the excess biochar produced. Furthermore, the team estimated that technology reduces CO2 emissions by 80% by avoiding the incineration of this waste stream. The technology moreover can be applied to other residues that contain at least a 30-40% cellulose fraction, obtaining similar results.
Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).
