Abstract :

The increasing concerns over the depletion of fossil resources and its associated geo-political issues have driven the entire world to move towards sustainable and alternative forms of energy and resources. Researchers all over the world are trying to develop processes to utilize waste (solid, liquid and gas) and renewable resources as they do not cause the climate change problems for the production of energy. Solar, wind, tidal, geothermal energy etc. can be used for the production of power/ electricity but the organic carbon required for the production of liquid hydrocarbons cannot be obtained from the above. Biomass or bio based products and plastics are the major components of municipal solid waste, which is a good source for the carbon for production high value hydrocarbons including transportation fuels and petrochemical feedstock. Biomass is the only renewable and sustainable source of organic carbon which can be obtained from any living or recently living biological material. Thermo-chemical methods of conversion have some advantages and are complementary with bio-chemical routes, as the thermochemical methods requires shorter processing times, flexibility in feed handling, complete utilization of feedstock, wide range of product slate etc. Under the umbrella of thermo-chemical methods, several processes can be utilized depending on the feedstock availability/ characteristics and end product requirement. Pyrolysis forms the basis of all thermo-chemical methods of conversion and can be carried out in different reactors with different operating parameters. Slow pyrolysis can be carried out in decentralized units which can be used for the production of hydrocarbons and electricity. Fast pyrolysis can be used when the production of bio-oil is required in huge quantities. Hydropyrolysis followed by hydroconversion will lead to the production of fungible hydrocarbons in a single step and self-sustaining manner. Carbonisation can be carried out for the production of bio-char in large quantities which has several applications such as soil amendment, catalysts/ catalyst supports/ adsorbents etc. In case of biomass with high moisture content, hydrothermal liquefaction is the most suitable process as it does not require any energy intensive drying step. The inherent moisture present in the biomass under sub-critical conditions helps in hydrolytic cleavage of the macromolecular structure of the biomass to yield high value chemicals. Both natural (lignocellulosic biomass) and synthetic polymeric materials (waste plastics) In short, to make the integrated waste management concept a reality, hybrid processes have to be developed which can utilize various waste streams for the production of energy, commodity or high value chemical / fuels and to improve the overall economics.