Agricultural by-products have major potential

Environment and sustainability 17. jul 2021 2 min Professor, Group Leader Solange I. Mussatto Written by Kristian Sjøgren

Research shows that better and more environmentally sustainable utilisation of by-products from agriculture and related industries can be profitable.

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Brazil is the global leader in producing ethanol from sugarcane , but Brazil still does not have an ideal financially and environmentally sustainable plan to dispose of all the by-products of ethanol production.

However, an international study with participation from Denmark has found an answer.

The researchers analysed the energy potential of the vinasse from ethanol production and how much farmers can save by using biodigested vinasse as fertiliser instead of buying expensive commercial fertiliser.

The research results have been published in Science of the Total Environment.

“Our study shows that using the vinasse has great potential if this sector is regulated better. Biodigested vinasse can replace much of the potassium and nitrogen fertiliser that is currently spread on the fields and can also be used to produce electricity for many households,” explains a researcher behind the new study, Solange I. Mussatto, Professor and Group Leader, Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby.

Using by-products to produce electricity

Producing ethanol from sugarcane involves several steps.

Sugarcane juice is fermented into ethanol. Ethanol is then distilled, leaving vinasse as a by-product.

Distilling 1 litre of ethanol results in about 12–20 litres of vinasse.

Vinasse used to be a problematic by-product of ethanol production, but today it can be used to fertilise fields and produce electricity, with the vinasse decomposing anaerobically, forming methane to be used in power plants to generate heat or electricity.

Nevertheless, vinasse is not utilised optimally.

Analysing the potential of vinasse

Solange I. Mussatto and colleagues analysed how to optimally use vinasse in Campinas, Brazil, where ethanol production is an important industry.

In Campinas, annual vinasse production could reach 23. 8 million m3, which can have an enormous environmental and energy potential if the vinasse is used properly as fertiliser and to produce electricity and heat.

The researchers obtained data for ethanol production from many facilities and examined the potential contribution of vinasse in agriculture and in the energy sector.

The researchers also evaluated the anaerobic digestion of vinasse to determine the energy potential for methane production and analysed the potential for using the residual by-product after methane production as fertiliser.

Solange I. Mussatto indicates that regulating the use of vinasse is crucial so that farmers benefit from using it in their fields without harming the environment and that vinasse is utilised for energy production when possible.

“Vinasse is an underutilised by-product today. Determining the potential is therefore relevant, including showing how to exploit this potential both by farmers and at the local and regional levels,” says Solange I. Mussatto.

Major environmental and economic potential

The experiments and calculations show that vinasse has the potential to greatly benefit the climate, farmers and the economy.

Anaerobically digesting all the vinasse in Campinas to produce methane could produce enough electricity to supply 103,000 residents of Campinas, almost 10% of the population.

In addition to the economic perspective, utilising vinasse to produce electricity would also reduce annual carbon dioxide emissions from Campinas by almost 36,000 tonnes.

The by-product after methane production can then be used to fertilise fields.

Overall, biodigested vinasse from ethanol production can reduce the total need for nitrogen, phosphorous and potassium in the fields by 30%, 1% and 46%, respectively, reducing carbon dioxide emissions by 111,877 tonnes per year.

Utilising the by-products following methane production in agriculture will also comply with local environmental laws and will not strain the environment further.

“We have shown that we have the technology to utilise vinasse more efficiently and how vinasse can contribute to both the economy and the environment, reducing carbon dioxide emissions and the need for fertiliser,” explains Solange I. Mussatto.

Applying the knowledge to Denmark

Solange I. Mussatto explains that, although the research was carried out in Brazil focusing on sugarcane, it is also relevant in Denmark and other countries.

Just as Brazil has vinasse, Denmark has many by-products from agriculture and related industries that are not utilised optimally, including by-products from breweries and even feathers from the poultry industry.

None of these potential resources are currently being utilised for valuable applications, but Solange I. Mussatto’s research group is working on projects to determine the potential of various types of residual products and how to better utilise the by-products to benefit the economy, the environment and society.

“Globally, many by-products are not being utilised. We found solutions for how vinasse can be utilised more efficiently, but we are also focusing on several other types of by-products from agriculture and related industries that can also be better utilised,” concludes Solange I. Mussatto.

The Biomass Conversion and Bioprocess Technology (BCBT) group is a leading research group at the Technical University of Denmark, dedicated to develop...

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