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examBoard: Cambridge
examType: IGCSE
lessonTitle: Energy from Waste Products
Every day, humans produce enormous amounts of waste. Rather than sending all this rubbish to landfills, we can actually use it to generate energy! This approach helps solve two problems at once: reducing waste and creating renewable energy sources.
Key Definitions:
Many different types of waste can be converted into energy:
Converting waste to energy offers several benefits:
There are several ways to convert waste into useful energy. Each method works best with specific types of waste and produces different forms of energy.
The simplest and most common method is burning waste directly to produce heat, which generates steam to power turbines and create electricity.
Waste is burned at high temperatures (850-1200°C) in specially designed furnaces. Modern incinerators have sophisticated pollution control systems to clean the emissions before they're released.
Large plants that burn mixed municipal waste with minimal pre-sorting. They can process hundreds of tonnes of waste daily and power thousands of homes.
Waste is processed to remove non-combustible materials, then shredded to create a more uniform fuel that burns more efficiently than raw waste.
These methods use microorganisms to break down organic waste, producing biogas that can be used for heating or electricity generation.
Organic waste is placed in sealed, oxygen-free tanks where bacteria break it down, producing biogas (mainly methane and CO₂). The biogas can be burned to generate electricity or refined into biomethane for use in the gas grid or as vehicle fuel. The remaining material, called digestate, can be used as fertiliser.
As waste decomposes in landfills, it naturally produces methane. Instead of letting this powerful greenhouse gas escape into the atmosphere, pipes can be installed to capture it. The collected gas is then cleaned and used to generate electricity or heat.
These technologies convert waste into gas or liquid fuels through controlled heating processes.
Waste is heated with limited oxygen to produce syngas (a mixture of hydrogen, carbon monoxide and methane). This gas can be burned to generate electricity or converted into liquid fuels.
Waste is heated in the complete absence of oxygen, breaking down into gas, liquid (bio-oil) and solid (char) components. Each can be used as fuel or further refined into other products.
Uses extremely high temperatures (up to 5,000°C) created by plasma torches to break waste down into its basic elements. This produces syngas with very little ash or other by-products.
This state-of-the-art facility processes up to 214,000 tonnes of household waste annually that would otherwise go to landfill. The plant generates enough electricity to power approximately 22,000 homes and has reduced Leeds' carbon emissions by 62,000 tonnes per year. The facility uses advanced combustion technology with sophisticated emissions control systems to ensure minimal environmental impact. Heat from the process is also captured and used in a district heating network, providing affordable warmth to nearby buildings.
While energy from waste offers many benefits, there are also environmental factors to consider:
The waste hierarchy is a ranking of waste management options according to what is best for the environment. Energy recovery sits in the middle of this hierarchy:
This means that while energy from waste is better than landfill, we should prioritise preventing, reusing and recycling waste where possible.
Sweden has been so successful with its waste-to-energy programme that it has run into an unusual problem: it doesn't have enough rubbish! The country now imports nearly 800,000 tonnes of waste from other countries to keep its 33 WtE plants running. Sweden recycles about 50% of its waste and converts about 49% to energy, sending less than 1% to landfill. This shows how effective a combined approach of recycling and energy recovery can be in creating a nearly zero-waste society.
As technology improves and environmental concerns grow, the waste-to-energy sector continues to evolve:
Energy from waste represents an important part of sustainable resource management. By treating waste as a resource rather than a problem, we can reduce environmental impacts while generating valuable energy. However, it works best as part of an integrated approach that prioritises waste reduction, reuse and recycling, with energy recovery capturing value from materials that can't be managed in other ways.
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