Genetically engineered carbon capture

Each year humans release nine gigatons of carbon into the atmosphere in the form of 33 gigatons of carbon dioxide. While some of this is absorbed by terrestrial and marine systems, around four gigatons remains in the atmosphere. Researchers from Lawrence Berkeley National Laboratory are attempting to publicly raise the question of whether genetic engineering may hold the solution to long term storage of this excess carbon [Jansson et al., (2010) BioSci 60, 685].

 

Prof. Christer Jansson and coworkers point out that plants can help reduce atmospheric carbon in two ways: either by storing the carbon as biomass, or by growing biofuels. To successfully implement the former approach it is vital that plants with extensive root systems are grown, as any above ground biomass will release carbon back into the atmosphere when the vegetation decays. In this regard perennial plants such as grasses are ideal.

 

According to the study, improving the long term carbon capture of plants means focusing on three key areas: enhancing the uptake of CO₂ through the photosynthesis process; raising the amount of carbon displaced into “low turnover” systems such as cell walls; and increasing the amount of carbon transferred to root systems.

 

If we are to improve the uptake of CO₂, genetic engineering may be the key. Previous studies have demonstrated that by modifying the canopy of plant leaves, significant improvements to light uptake may be obtained in the early morning and late afternoon. However, the biggest problem is that plants are limited in the amount of sunlight they can usefully absorb by the carboxylation reaction. Jansson et al. point out that most plants saturate at 25 % of full sunlight. However, some plants such as the grass Miscanthus (known as C₄ plants) undergo a different photosynthesis process. These plants are both more efficient and can operate at higher light levels before saturating.

 

Unfortunately C₄ plants are only more effective at higher temperatures, and so genetic engineering offers two possible solutions. The first is to raise the saturation limits of C₃ plants by incorporating C₄ enzymes, while the second is to engineer C₄ plants into being more efficient at low temperatures.

 

The study estimates that by 2050, should these and other genetic alterations be implemented, carbon sequestration by plants could increase by several gigatons. Although human emissions may increase in this time, it would no doubt go along way toward relieving the carbon crisis.