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Converting Waste To Electricity

Opinion – Andy Loader

The Auckland region produces approximately one and a half million tonnes of waste per year that mostly goes into landfills. Collection and disposal of that waste stream is one of the largest services that the Auckland City Council provides to its ratepayers. …

The Auckland region produces approximately one and a half million tonnes of waste per year that mostly goes into landfills.

Collection and disposal of that waste stream is one of the largest services that the Auckland City Council provides to its ratepayers.

So why should we look at converting that waste stream into electricity?

Let’s look at some known facts around waste management and electricity generation.

Fact: Existing landfills are rapidly reaching their full capacity.

Fact: Landfilling is not the best practical method of dealing with the waste stream.

Fact: Landfilling produces large quantities of methane gas over long periods of time.

Fact: Methane gas is one of the worst of the greenhouse gases.

Fact: Landfills produce an ongoing liquid leachate of toxins and pollutants over long periods of time.

Fact: If the landfill liner is compromised then this leachate will leak into the surrounding environment and create an ongoing toxic pollution problem.

Fact: Using waste to produce electricity produces approximately 90% reduction in the waste volume.

Fact: The latest technology for incineration of waste produces carbon dioxide gases.

Fact: Carbon dioxide is one of the lesser greenhouse gases compared to methane and according to Emissions Trading Scheme criteria, this CO2 is accepted as coming from organics classified as renewables.

Fact: We are currently burning over one million tonnes per year of imported coal from Indonesia to produce electricity, from the Huntly power station.

Fact: We currently use large quantities of natural gas to supplement our hydro power when the lake levels are reduced from drought conditions.

Fact: Without that thermal generation capacity the lights will start to go out in rolling blackouts.

Fact: Our supply of natural gas is rapidly running out and the government has banned further exploration for oil or gas.

Fact: The government has committed to stopping the use of fossil fuels and converting to electricity use instead.

Fact: Given the current focus on the use of electricity to replace the use of fossil fuels the demand for electricity is going to increase exponentially.

Fact: New Zealand currently does not have the capacity in sustainable generation of electricity to stop the use of thermal generation outright.

Fact: If the hydro lake levels drop significantly due to weather effects and the wind doesn’t blow at that time then we will need to rely on thermal generation or see rolling blackouts as has happened in the near past.

Fact: When the natural gas supply has exhausted, which is predicted to happen in the very near future, then we will be relying on coal fired generation (whenever sustainable generation is not available) as the only option under the present system.

Fact: We don’t currently have the infrastructure available to rely on sustainable generation at all times.

Fact: Without the use of thermal generation there will be times when the demand for electricity will outstrip supply and then we will be faced with rolling blackouts.

Fact: The Auckland region generates approximately 150Kg per person each year of general waste that mostly goes into landfills.

Fact: A 2010 report showed that an average Auckland refuse bin contents which mostly goes to landfill is made up of the following weights:

• 15% recyclables

• 35% refuse

• 40% food waste

• 10% green waste

Fact: Auckland city has over the last few years experienced unprecedented population growth, which has increased the requirements for electricity supply, and correspondingly contributed to more refuse to the waste stream.

Fact: We will never completely eliminate waste from our lives and therefore will always need to deal with a residual level of solid waste.

Fact: A significant percentage of this residual waste stream can be used to convert it to electricity generation and therefore prevent the need for it to go to landfills.

Converting waste to electricity is recognised as a proven and reliable technology which has been used in Europe, North America and Japan for decades.

There are over 500 operational plants in Europe alone, many of which are in and around major cities such as Paris, Zurich, Vienna and London, which are converting waste into energy.

Many of these cities have the process of generating energy from waste as a key component in their waste management hierarchy thereby reducing their landfill requirements almost to zero.

The residual waste that would otherwise consigned to landfill uses technology to generate energy from the controlled burning of that waste. The generation plants burn the waste and convert the released heat into steam which is used to generate electricity. The latest filtering technology is used to ensure that the incineration systems comply with all emissions standards from their exhaust chimneys.

Modern waste incineration plants have the flexibility to provide energy as steam or electricity and can switch between the two during the plant’s operation as required.

According to the Waste Hierarchy, the recovery of energy from waste is the next preferred method after recycling. Disposal to landfill is the least preferred method of waste management, yet it is the most widely used in Third World countries, and is current best practice in New Zealand.

So why should we look at converting that waste stream into electricity now?

We are facing rising power prices, increasing energy demand and the eventual closing down of the natural gas supply which provides baseload power and solid waste levels are increasing alongside the increasing population.

The changing climate means there is the distinct possibility that our ever reliable sustainable hydro generation may become a lot more unreliable with the changing weather patterns and we will not have enough excess capacity to cope with the present demand under those circumstances, let alone with the projected increased demand from the current government policies.

Why should we look at Huntly Power Station for converting waste into electricity?

The practical considerations which led us to suggesting that Huntly would be the logical choice were as follows:

• There is an existing operating power station that can be converted to use waste to generate electricity

• The possibility of using existing or additional rail infrastructure to enable waste transport to the plant by train

• The road infrastructure to the plant is well organised for truck traffic with major arterials bypassing residential areas.

• Grid electricity connections available with sufficient capacity

• Land available for development of the infrastructure required to process the waste stream.

• Area available to dispose of the fly ash produced as part of the process in rehabilitation of existing opencast coal mine sites.

• Access to local workforce.

• There is area available close to the Huntly Power Station that could be used to take advantage of the energy produced from the incineration of waste such as the use of steam heat for food production etc.

Given all of the above it seems patently obvious that we should be investigating the conversion of waste into energy for generation of electricity and we should be doing so immediately.

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