Waste from the citrus industry can provide biogas and valuable products for a range of industries, according to a doctoral thesis at the University of Borås in Sweden.
“The citrus industry creates so much waste that it corresponds to between 40 and 60 percent of the total citrus mass,” said Lukitawesa Lukitawesa, who recently defended his doctoral thesis at the University of Borås. “Imagine how much waste there is when the world’s total citrus production is 132 million tons of fruit per year. Therefore, it is extremely important to recycle what is thrown away.”
Lukitawesa’s research aims to develop methods for how citrus waste can be made into methane/biogas and a building block chemical for biocomposite of plastic. This is a major challenge, as the waste contains toxic citrus peel oil and thus becomes difficult to use in anaerobic (non-oxygen demanding) digestion. However, the study shows that it is, in fact, possible.
Toxic organic material such as fruit waste has traditionally been disposed of in landfills. But anaerobic digestion can be used to produce biogas or fatty acids, all for the sake of the environment and the climate. The solution that Lukitawesa highlights is anaerobic digestion in two steps, using a membrane.
In the first part of the doctoral thesis, biogas production from citrus waste was studied. This is something that can reduce environmental destruction and increase the production of renewable energy.
“Afterwards, we realized that even the direct product of the first stage of digestion, fatty acids, is valuable,” said Lukitawesa.
The second half of his doctoral thesis deals with how bioreactors can produce volatile fatty acids when loaded with a large amount of citrus waste. Previous research in the field has focused primarily on loading a smaller amount of citrus waste.
Volatile fatty acids today have a wide range of uses within industry and are included in an array of products, from medicines and food to paints and plastics. But the volatile fatty acids that are normally used industrially are fossil-based; here, we have a climate-friendly alternative.
Lukitawesa says he wants to do more research on how citrus waste can produce volatile fatty acids. His doctoral thesis has raised new questions and has laid the foundation for new important studies.
Source: University of Borås
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