Sweet Sorghum, Sorghum bicolor (L.) Moench, is a native of Africa, south of the Sahara Desert. It is a drought-resistant, heat-tolerant member of the grass grass family, with an efficient C4 photosynthetic pathway. Nowadays, it is grown on all the continents (except Antarctica), as well as in northern hemisphere countries. Its cultivars have been adapted to a variety of climate and soil conditions.
Adaptable, efficient and economic
Sweet Sorghum can be grown in soils ranging from clay to loam (i.e. soil that is composed mostly of sand and silt, and a smaller amount of clay) with neutral to high pH (5 to 8.5). Best growth is achieved on loams and sandy loams. Sweet sorghum has also been called "a camel among crops", owing to its wide adaptability, its marked resistance to drought and saline-alkaline soils, and tolerance to waterlogging. It shows best growth in in semi-arid areas with 450–800 mm rainfall and at an altitude range from sea-level to 1,000m. Sweet Sorghum uses ⅓ of the water of sugarcane and ½ of the water of grain crops. It doesn't require excessive irrigation and can survive long, hot summers. One special adaptation is that in a drought it can go into a state of “plant hibernation”, with a very low metabolic rate and little water use. Then when soil moisture returns, the plants start growing again, from where they were before the drought. In addition, it has a high nutrient use efficiency (⅓ that of sugarcane), resulting in a production costs that is ½ that of sugarcane production. The sweet sorghum growth cycle is short (about four months) facilitating double cropping. It can be easily grown from seeds and its production can be completely mechanised.
Growing Sweet Sorghum feedstock for biorefineries means in long-term profitable farming.
Sweet sorghum looks much like maize without the ears. Instead of tassels on top, it has clusters of many seeds. The seeds are small and round about 1.5mm in diameter. Each plant grows 2 to 3 m tall and 25 to 50 mm in diameter at the base of the stalk.
DalinYebo's µ-BioRefinery: Converting Sweet Sorghum into Furfural and Energy.
Grain: Animal feed, (gluten free) flour and alcoholic liquors
Juice: Liquid sweeteners and animal feed
Bagasse: Animal feed, dietary fibre and biomass pellets.
Sweet Sorghum biorefineries
There are a few combinations suggested, with most of them focused on fuel ethanol production. Researchers have also demonstrated the conversion of sweet sorghum into methane and hydrogen gases or diesel and other chemicals, also using the lignin fraction. Sweet sorghum is used as an alternate crop with sugar cane to fill the gap in sugar cane production, when sucrose content drops too low for harvesting. In Brazil this happens during a period of 3 months every year and sweet sorghum keeps their bioplastics plant operating 12 months of the year.
We have tested and identified varieties that are ideal as feedstock for a biorefinery with integrated ethanol & furfural production, ..
.. whilst there are other cultivars that have been developed e.g. as a source for animal feed, or for syrup and sugar production. There are ongoing breeding programmes that look at early maturity, disease resistance, drought resistance etc. or at cross-breeding of sweet sorghum with other 'grasses' to develop the next generation energy-feedstock for biorefineries.
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This article is part of a series on "biomass for furfural" production, which provides our clients with updates and analysis on the fundamentals and competitiveness of a variety of feedstock.