Biofuels production using plasma technology

Use of ozone-generated plasmas to delignification of biomass was tested in laboratory scale by various groups for different types of biomass as cane sugar bagasse, wheat straw and Japanese cedar. The technology is effective superior to conventional pre-treatment methods in terms of conversion efficiency of enzymatic hydrolysis, but more studies about the energy efficiency and economic point of view is needed. In this sense, the research to obtain more effective ozonizers could enable economically viable processes.

Ozone interaction mechanism with the biomass is relatively well known, but more research is needed to unravel the influence and the role of other radicals (e.g. singlet states of atomic and molecular oxygen, OH, H2O2) in biomass degradation processes.

Another strategy is to treat the biomass in direct contact with the plasma, both in gas phase or in liquids. In this case, depending on the physicochemical properties of plasma, several types of effect on biomass could be observed in addition to the delignification. Further studies are needed, which could make an important contribution in the field of biomass engineering processes, such as the discovery of new methods for obtaining high added value products. The experimental investigation of plasma interaction mechanisms with biomass is another field to be explored, and experimental techniques of monitoring in real time or retrospectively the effect of plasma on biomass need to be developed.

While many alternative sources of renewable energy have the potential to meet future demands for stationary power generation, biomass offers the most readily implemented, low cost solution to a drop-in transportation fuel for blending with and/or replacing conventional diesel via the bio refinery concept, illustrated for carbohydrate pyrolysis/hydrodeoxygenation or lipid transesterification.

Heterogeneous catalysis has a rich history of facilitating energy efficient selective molecular transformations and contributes to 90% of chemical manufacturing processes and to more than 20% of all industrial products. In a post-petroleum era, catalysis will be central to overcoming the engineering and scientific barriers to economically feasible routes to alternative source of both energy and chemicals, notably bio-derived and solar-mediated via artificial photosynthesis.

The conventional heterogeneous catalysts involved in biodiesel production include mixed metal oxides, alkaline metal oxides, ion-exchange resins, sulfated oxides and immobilized enzymes. Heterogeneous catalysis has emerged as the preferred alternative for biodiesel production because the products are easy to separate, the catalysts are reusable, and the process is environmentally friendly. However, this method suffers from limitations, such as mass transfer problems, high cost and low catalyst stability, that diminish its economic feasibility and low environmental impact on the entire biodiesel process.

Carbon nanotubes (CNTs) appear to be a promising catalyst support for biodiesel production due to their ability to overcome the limitations faced by conventional heterogeneous catalysts. Thus, another point is the proposal of the application of functionalized CNTs as catalyst support in biodiesel production, investigating issues such as the limitations encountered by conventional heterogeneous catalysts, the advantages offered by functionalized CNTs and possible methods to functionalize CNTs to serve as catalyst support in biodiesel production.

Another promising catalyst is the graphene sheets. Functionalized CNTs and graphene sheets  can easily be produced by plasma routes and also hold great potential to be a breakthrough technology in the biodiesel industry.