Growing biofuels in marginal land

Growing biofuels could help reduce net carbon emissions, but it’s not a simple solution. “[I]n some geographical regions there is intense competition for land as we are also faced with the challenge of providing food security to the world’s growing population,” said da Costa and colleagues in their Annals of Botany article Nutrient and drought stress: implications for phenology and biomass quality in miscanthus. “Using food crop residues as feedstock for biorefining could partly alleviate this competition for land use. A complementary strategy to optimize land use is to cultivate dedicated biomass crops on under-utilized lower-grade agricultural land, also referred to as marginal land. This would avoid displacement of crops currently used for food and feed production from productive agricultural land on marginal land may avoid losing better land needed for food crops, but it will be important to choose the right biofuel crop for the marginal land…”

Marginal lands will have stresses for plants. They may be soils lacking in nutrients, or possibly under-watered. For this reason, it’s not enough that a plant is a good source of energy. It has to remain a good source of energy, even under stress. da Costa and colleagues examined three genotypes of miscanthus, Miscanthus sinensis, Miscanthus sacchariflorus and Miscanthus × giganteus, so see how they reacted to poor conditions.

“While water and nutritional stresses are mostly studied in isolation, they are often experienced in combination, particularly when crops are grown on marginal land. For this reason, and when projected changes in climate are considered, understanding the combined effects of these stresses is important,” said da Costa and colleagues. They kept an automatic eye on the plants, using the automated imaging facilities at the National Plant Phenomics Centre in Aberystwyth.

Automated imaging is a rapidly advancing area of research and da Costa et al.’s paper has already led to new research demonstrating cheaper ways of tracking growth in 3D. For da Costa and colleagues, the automated imaging was a tool for watching plant responses to stresses, both separately and in combination with each other.

The goal was to see how the conditions affected the building of cell walls, with their useful payload of sugars. They found there were distinct differences in how the plants responded to the difficult conditions. “The combination of different irrigation and nutrient treatments had a significant effect on the release of sugars from the cell-wall matrix of leaves and stems, highlighting the importance of genotype–environment interactions,” said da Costa and colleagues. “The changes in cell-wall features induced by different abiotic environments that underpin observed sugar release differences have not yet been identified but possibly result from changes in the fine structure of cell-wall constituents. Future studies, using more sophisticated methods for cell-wall analysis and improved measures for nutrient levels and compost texture, could address such changes in more detail.”

da Costa has since worked with colleagues to take a closer look at the cell wall. They argue that there is no single ideal cell wall and instead targeted breeding should produce cells walls with specific biorefining goals. This variable is a problem mentioned in closing the Annals paper. “While miscanthus has potential for liquid-based biofuels, future work will also need to address other quality measures associated with the miscanthus biomass-based value-chain products, such as combustion, biogas and other biomaterial requirements…”

While miscanthus may have a role to place in future energy policy, that role will depend on what the targets of the new energy economy are.