The world generates millions of tons of agricultural waste every DAY!
A good portion of this waste is just…wasted. Left to rot, or worse, burnt!
Instead, can all these agri and crop waste be put to use to generate power?
Well, to a large extent, yes. Most of the agricultural waste have the inherent potential to be a feedstock for power generation.
But firstly, let us look at some of the prominent types of agri-waste available worldwide:
- At the farm
- Plant stalks, straw, pith – Typically such waste are generated and available at the farms themselves. Examples include cotton stalks, mustard stalk, soy stalk, paddy straw, sugarcane trash…
- At the processing facility
- Pre-processing – These wastes are also typically generated at crop processing facilities before the crop is processed. Examples of these agri waste include ground nut shells, coconut shells, rice husk, corn cobs…
- Post processing – These wastes are generated after a crop has been processed, typically in an industrial or factory setting. Examples of such waste include soybean waste or castor seed waste (after oil extraction at a soy oil refinery), castor seed waste(at a castor oil refinery), saw dust (after the wood has been sawed at saw mills), bagasse (after the sugar has been extracted from the sugar cane at sugar mills)…
- Post the product use
- While most of the waste from agriculture and crops are generated at the farm level or at the processing facility, waste from these are also generated post end use, though at much smaller scales. Examples could be fruit and vegetable peels discarded at houses and commercial establishments, coffee waste where coffee powder is used etc.
The above ones form the main categories of agriculture and farm waste available.
Which of the above mentioned waste can be used to generate power, with currently available technologies?
In theory, all the above waste can generate power, with the currently available technologies.
In practice however, only a subset of these wastes lend themselves to being economically viable as power generation sources.
Agricultural waste that are woody and dry can be easily used for power generation (woody stems for instance), and overall have excellent economic feasibility
The not-so-woody waste such as rice husk, rice straw, sugarcane stalks etc can also be used to generate electricity, but we may have to be more selective in their use – only some types of power generation equipments might be able to support these.
Some of the feedstock might need significant processing (chipping, crushing, drying) before they can be used in boilers or gasifiers. The more the processing required, the less its economic attractiveness, the costs for processing could sometimes be quite formidable – drying, for instance, is an energy intensive process incurring significant energy costs.
So, the cost of power generation varies depending on the type of agri waste – the cost could be lower if one uses dry, woody waste as these can be readily used without the need for much processing, while use of agri waste such as paddy straw could require significant processing before being used in a boiler. Some of these feedstock could be more suitable for the latest types of boilers and gasifiers, and as a result could generate much better power conversion efficiencies overall.
The bottomline is this: While most agriculture and crop waste have the potential to be used as a feedstock for power generation, which feedstock is economically and logistically more favourable depends on the scale of the biomass power plant as well as the equipment and processes used for power generation.
Having dealt with a number of biomass power companies, what I observed is that most companies have a basket of at least 3-4 agri waste feedstock for their fuel. Agricultural waste collection and logistics are fairly unorganized, and this makes it critical for power companies depending on such feedstock to spread their supply chain risks, reducing their dependence on any one feedstock alone.