Recover energy from biogas produced at MSW landfills
A MSW landfill generates two types of wastes:
- Leachates which are effluents containing contaminants produced from rain percolating through solid wastes
- Biogas which is produced as a result of chemical reactions of solid wastes buried in the landfill.
All MSW landfills are required by law to treat both types of wastes, so in this post we will see how biogas can be recovered and reused as an energy source for the treatment of leachates, without incurring huge costs, which would be involved in the transformation of biogas into energy or fuel for other uses.
Is biogas energy recovery profitable?
Recover energy from waste biogas transformation can become profitable since this landfill generated biogas can be reused for two main purposes:
- To generate thermal and electric energy. This process can be carried out by motor-generator units, or biogas turbines
- To be directly used as fuel after purification, serving as:
- Fuel for biogas boilers
- Injection into natural gas network
- Automotive Fuel
The challenge faced by most MSW landfills is that the installation of the machinery necessary for the transformation of biogas into energy or fuel is too costly and, above all, unprofitable. This is because the amount of biogas generated in most landfills is not enough to produce a really significant amount of energy that can be reused to offset the investment made in machinery.
On the other hand, it is frequently the case that even when landfills are capable of producing large amounts of electrical energy, no electricity transmission towers are located nearby to which the generated energy can be transferred.
A possible solution to this would be not to transform biogas, but to burn it using flares instead, so that it is not emitted into the atmosphere. However this would not be the most appropriate choice, since this source of energy would be wasted.
A smarter solution for those landfills that do not generate a large volume of biogas would be to reuse it as a source of energy to drive the landfill processes.
The biogas as an energy source for leachate treatment
There are several technologies that can be applied to MSW landfill leachates treatment, however the method of vacuum evaporation, combined with or without pre- or post- reverse osmosis, has proven to be nowadays the most efficient to minimize leachate and obtain purified water suitable for discharge.
The energy needed by the vacuum evaporator to function may come from the landfill’s biogas. The use of a simple and economic system, such as a boiler with a biogas burner, will make it possible to obtain sufficient energy to ensure the proper functioning of the evaporator.
In this way, the benefits are threefold:
- A source of energy is reused
- The energy required to operate the vacuum evaporator, intended to treat the leachate, is obtained at zero cost
- Biogas is reused by a much more profitable method in the case of landfills which do not generate biogas in sufficient quantities to justify the huge investment involved in its transformation into electricity, thermal energy or fuel