Sweet Sorghum Promising for the Environment

Sweet sorghum can be used to produce biogas, biofuels, and novel polymers. In addition, it can help replace phosphate fertilizers. A new sweet sorghum variety developed at Karlsruhe Institute of Technology (KIT) accumulates particularly high amounts of sugar and thrives under local conditions. As the scientists reported in the Industrial Crops & Products journal, sugar transport and sugar accumulation are related to the structure of the plants' vessels. This was the result of a comparison between sweet and grain sorghums.

As the world's population grows, the demand for food, raw materials, and energy is also on the rise. This increases the burden on the environment and the climate. One strategy to reduce greenhouse gas emissions is to grow so-called C4 crops. These carry out photosynthesis particularly efficiently, are therefore more effective in fixing carbon dioxide (CO₂), and build up more biomass than other plants. Usually, they are native to sunny and warm places. One of the C4 plants is sorghum, also known as great millet, a species of the sorghum genus in the sweet grass family. The varieties that are particularly rich in sugar are called sweet sorghum (Sorghum bicolor L. Moench). Other varieties include grain sorghum used as animal feed. Sorghum can be grown on so-called marginal land, which is difficult to cultivate, so it does not compete with other food or forage crops.

A new sweet sorghum variety called KIT1 has been developed by Dr. Adnan Kanbar in the Molecular Cell Biology Division research group headed by Professor Peter Nick at the Botanical Institute of KIT. KIT1 accumulates particularly high amounts of sugar and thrives especially well under temperate climate conditions. It can be used both energetically, i.e. for the production of biogas and biofuels, and as a base material for the production of novel polymers. The estimated sugar yield per hectare is over 4.4 tons, which would correspond to almost 3,000 liters of bioethanol. In addition, the digestate produced during biogas production can be used for fertilizers to replace phosphate fertilizer, which will soon be in short supply.