Valorization: A process for sustaining life
Valorization could be defined as a process of converting waste into valuable merchandise which could be industrially important chemicals, fuels, materials, etc. Waste valorization is not a new concept, it has been in existence for long enough, it has now been brought up by the society due to the fast deprivation of natural resources and the increased waste generation worldwide. Many of the waste valorization strategies have been implemented a few of which are as follows:
Flow chemistry is already being in use by various industries for processing the waste into valuable products particularly in the food industries. Few of the pros of continuous flow chemistry are the ease of scale up and high yield. The cons are huge energy requirements for degrading highly stable bio-polymers and recalcitrant compounds (ex. Lignin).
The second most used strategy for valorization is pyrolysis, a method in particular that has been used for generation of bio-oils. Bio-oil has a low viscosity index and is a mixture of short chains of ketones, aldehydes and carboxylic acid. There are a few reports of furniture waste saw dust being converted into bio-oil by using a fluidized bioreactor which could yield 57% bio-oil as reported by Hoe et al (2014).
The third strategy is ‘Microbial bio degradation’ of waste in order to generate valuable products (Biofuels, Biofertilizers, etc.). Bio conversion has been in the picture for more than a decade now, this is considered to be a green method for converting a waste into commercially and industrially valuable products. One of the examples of this could be generation of bio-fuels from agricultural waste.
Biofuel- Valorization of agriculture waste-
Generation of bio-fuels from crop has is now been a technology that has failed to pick up as much momentum as we would have liked , in comparison microbial fuels show much greater promise.
Many microbes such as algae, bacteria, fungus and yeasts have the ability to accumulate oil, such microbes are known as oleaginous microbes. Microbial oils can be used as a potential feedstock for the generation of biodiesel in the future. The extent of lipid accumulation of an oleaginous microbe is determined by its genetic constitution. The yield of SCO can be increased by genetic manipulation as well as by varying its growth parameters.
One of the main strengths of India is its agriculture sector, various amounts of waste is generated in this sector in day to day basis, which is either used as feedstock for cattle, some is used as fuel and other is being just dumped into landfills. By valorizing the waste material generated in this sector for the production of Biofuels could be beneficial. Here the question of crop for food vs fuel can be solved by utilizing the waste itself for generation of bio-fuels.Various substrate like corn cobs, sugarcane and beet molasses, grain husk, cotton stalk waste, oil cake meals, etc. still have high nutritional value, such agricultural by products can be used as a whole for production of the microbes which could accumulate lipids generally termed as oleaginous microbes, further these lipids (single cell oils) can later be used as a feedstock for generation of biodiesel.
Microbes which are reported oleaginous microbes and can be used for production of biofuels with favorable substrate are :
Bacteria- Bacillus subtilis (sugarcane molasses waste), Rhodococcusopacus (Corn cob);
Fungus- Aspergillus terreus (Pineapple peels, sugarcane molasses,oil peat), Mucor spp. (oil peat, cheese whey), Colleototricum sp. (Beet molasses, orange wastes), Alterneria spp. (Grain husk)
Yeast– Yarrowia lipolytica (Saw dust and grain husk waste)
Actinomycetes- Thermomonospora fusca and Streptomycetes spp.(Wheat bran and Oatmeal husk) They are known to accumulate approximately 70% of lipid under stress condition
Extensive disposal of waste is deteriorating landfills in many parts of the world, the landfill can be used for better purposes such as waste valorization. Joint efforts to form a green technology across various disciplines such as bioengineering to chemistry, biotechnology to environmental sciences and economics as well could lead towards the betterment of Mother Nature. A step towards sustainable development by waste valorisation could be a step to healthy and green future.