There has been growing interest in increasing the industrial use of cassava starch, said researchers at the Swedish University of Agricultural Sciences and China Agricultural University. However, this does not mean there is a need to expend food stocks or occupy more land to increase production, they said.
Instead they said that discarded cassava stems - currently removed and considered waste – should be used to their full potential. Ultimately, 30% or more of the dry mass of cassava stems could be used, although this current research has just used 15%.
Research leader Shaojun Xiong told FoodNavigator that the report's data is on the more conservative side of what he feels is eventually possible.
The researchers anticipate that if stems were to replace roots in cassava starch production by 2030 an extra 100 million people could be fed.
The report addresses three scenarios: stem starch extraction using a simple water extraction process, more high-tech extraction processes being implemented and finally assuming forecasts for increased cassava production.
"The cassava feedstock resources can be utilised more efficiently within the combined Food & Fuel concept where both starch and fuel production are increased and, in addition, waste is minimised when the stems are integrated into the combined starch and fuel model according to one scenario (starch + solid biofuel + biogas),” said the study's co-author Torbjörn Lestander.
“Very, very simple technique”
Xiong said that their study has only just begun to unlock the possibilities of extracting starch from cassava stems. He said that with more funding they could extract much more than the 15% extracted achieved with a “very, very simple technique using water...We wanted to free the possibility for those low income people. So that’s why we have used this very simply technique and in that case we got 15%. If we use advanced technology we can take more.”
Lestander added: “The technique is very simple. Just mill the stems into a powder and put it in cold water than [sic] the small starch grains will accumulate at the bottom (just like small stones) whereas the rest of the stem biomass can be removed.”
Cassava is very starchy and can be processed into flour or semolina (tapioca). It is a staple food for between 0.5-1 billion people in Africa, Latin America and Asia, wrote the researchers.
As well as food production, the study also looked at the potential to use the waste for bioenergy.
Source: GCB Bioenergy
Published online ahead of print, doi: 10.1210/jc.2013-1698
“Cassava stems: a new resource to increase food and fuel production”
Authors: W. Zhu, T.A. Lestander, H. Örberg, M. Wei, B. Hedman, J. Ren, G. Xie, S. and Xiong