Thermo-chemical conversion of biomass.

http://dx.doi.org/10.1016/j.biortech.2014.12.085 0960-8524/ 2014 Published by Elsevier Ltd. Energy in all forms is the basis of the development of mankind since beginning. Man used biomass based resources for his sustenance before the discovery of crude oil and detail understanding of its refining techniques. Now with the volatility in crude oil prices and its availability the world is again looking forward to cheaper sources of energy. To add on to the problems with crude oil, there is now this issue of climate change due to greenhouse gas emissions by the usage of fossil based resources. This has all the more accelerated the shift to using renewable and sustainable sources of energy. Electricity can be from solar, wind, ocean or tidal energy etc. but organic carbon is required for the production of fuels/ chemicals or petro-chemical feedstocks. Biomass defined as any biological material which stores energy by the process of photosynthesis is the only source of renewable and sustainable organic carbon. To overcome the issues of food vs. fuel, lignocellulosic biomass (biomass composed of cellulose, hemicellulose and lignin mainly) and algal biomass (from microand macro-algae) are now being used for the production of hydrocarbons. There are various techniques for the conversion of biomass which can be broadly grouped into biochemical and thermo-chemical methods of conversion. The thermo-chemical and bio-chemical methods of analysis have their own advantages and disadvantages. As of now, there are no commercially demonstrated biorefineries which have both thermo-chemical processes and biochemical processes. Some of the advantages of thermo-chemical methods of conversion over the biochemical methods of conversion are the reduced conversion time in the order of few seconds to couple of hours rather than few days in case of biochemical methods. In contrast to the biochemical methods, the thermo-chemical methods of conversion can convert the entire biomass without rejecting any component (lignin) and is not highly feedstock sensitive. It also produces a broad range of products which can be carefully separated for further use. There is an urgency to introduce the concept of biorefinery and biofuels into the market for several reasons under the umbrella of sustainability issues. Thermo-chemical methods are the fastest way to go as they can meet the local demand as per the local supply and also provide employment opportunities. The small scale systems can be operated in isolation using the locally available biomass and some of the products can be consumed onsite. The other products can be transported to a central facility or a centralized biorefinery which has higher capacity and sophisticated processes for upgradation to value added hydrocarbons. The thermo-chemical conversion of biomass has been gaining a lot of interest in the recent years which is evident by the increase in the number of articles being published on this topic. It is necessary to improvise the existing processes for the local applications in the form of fuel oil, burner oil or power generation sets. In this scenario, we felt the need for a special issue to report the recent advances on the various thermo-chemical methods of conversion of biomass conversion to various products. The issue aims to provide the reader a compilation of articles on various areas under the umbrella of thermo-chemical methods of conversion. Some of the topics covered are as follows