A bridge to sustainability

Since the challenge of climate change is huge, all solutions are needed to reduce greenhouse gas emissions and reach net-zero as early as possible. Towards this objective, biomass and energy from waste is considered a viable solution, only if certain conditions are met. Basically, biomass would be viable only if the right feedstock is used. If the wrong feedstock (such as fully grown trees or grains such as corn and sorghum) that require lots of inputs (such as fertilisers and groundwater) are used, biomass is not a good solution.

Biomass energy, methane digesters and energy from waste

Paul Hawken, the author of ‘Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming’ has called energy from Biomass a ‘bridge’ solution. It is a bridge between the world of 100 per cent energy from renewable sources and today’s world. He also calls it a ‘necessary’ though imperfect solution: necessary, because it would buy us time in the transition away from fossil fuels.

It is interesting to note that before the industrial revolution, biomass was the main source of energy across the world. It continues to be an important source of energy in many developing countries even today. Biomass is basically a product of photosynthesis, whereby plants use sunlight, carbon dioxide and water to make and store carbohydrates. This biomass converts into fossil fuels if left untouched for thousands of years. Biomass short circuits this process of fossil fuel formation and is used for energy by either direct burning or chemical conversion into liquid fuels or biological conversion into liquid or gaseous fuels or generation of power.

Biomass sources include wood and wood processing waste (firewood, saw dust, furniture waste and paper and pulp industry waste), agricultural crops and waste (corn, sorghum, switchgrass, woody plants and crops residue), usable municipal solid waste (paper, cotton, food) and animal manure and human sewage.

As noted in the Introduction above, biomass works only if the feedstock being used is appropriate. That is, the feedstock should be grown in a sustainable manner and use minimum inputs. A good example of appropriate biomass is switchgrass, which can be harvested for a long time before replanting is needed. Another example is short-rotation woody crops such as shrub willow and eucalyptus.

The top five countries using biomass energy in the world are Brazil (because of large sugarcane production, which is being converted into ethanol in a big way), China (which uses agricultural residue and waste), the US (which uses corn), India (which uses agriculture and animal waste) and Germany (which uses agricultural residue and industrial waste).

Waste to energy

Paul Hawken in his book mentioned above, informs that the waste to energy projects in the USA were basically waste incineration projects, which, in turn, were derived from the companies that used to make nuclear plants. These companies basically tapped the energy in all kinds of waste such as plastic, paper, foodstuff and junk, by incinerating it. Other ways of getting energy from waste is gasification, pyrolysis and plasma.

Waste to energy plants are popular in cities and help municipal authorities handle the thousands of ton of garbage in an efficient manner. If garbage were just to pile up, it would have to be buried in landfills, which in turn would emit methane: an even more polluting greenhouse gas than carbon dioxide. The US is the leader, burning 30 million tonnes of garbage annually. Many European countries such as Sweden, Denmark, Germany, Netherlands and Belgium also have waste-to-energy plants. In Europe as a whole, there were 480 such plants in 2022. Sweden is the leader in Europe, with 34 such plants, which process 2 million tons of trash annually. Sweden even imports 8 lakh tons of garbage for these plants. Sweden’s technology is also one of the best, with facilities for sorting garbage and scrubbing and filtering, so that all hazardous materials and gases are handled.

A related technique is one of ‘methane digesters’, wherein organic waste is tapped for energy, through the process of anaerobic digestion. More popularly known as biogas plants, these are popular in rural areas of Asia and Africa. In Europe, Germany leads the way with 4000 Megawatts of installed capacity of biogas plants.

Conclusion

Biomass, waste-to-energy plants and biogas plants are a useful way to reduce emissions of greenhouse gases if handled right. This is however a temporary solution, and more to buy us time to ramp up other renewables such as solar and wind. Biogas plants or methane digesters, will however continue to be an attractive solution for municipal bodies, as a way to handle tons of garbage as well as generate some energy in the process.

The writer is Additional Chief Secretary, Department of Mass Education Extension and Library Services and Department of Cooperation, Government of West Bengal