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The W2E plant in La Rioja Ecopark (Spain), designed and build by Acciona

The W2E plant in La Rioja Ecopark (Spain), designed and build by Acciona



W2E effective way to reduce emissions

Producing energy from urban waste is not an alternative to recycling, but is a complementary process in the search for increasingly sustainable environments, says David de Lara, Middle East Country Manager for Acciona Industrial

March 2019

The UAE has one of the highest waste generation rates, with each person in the country estimated to produce on average up to 2.3kg of waste every day and Dubai generates 8,200 tonnes of municipal solid waste per day, according to figures released in 2016 – that is 15 per cent above the global average. Therefore, it is a fact that managing these thousands of tonnes of waste that we produce every day is one of the most important challenges in order to preserve our environment.

In the case of solid waste, this is a triple challenge: firstly to reduce the quantity of this waste; secondly, to reuse the highest possible percentage of the waste produced; and lastly to recycle any waste that cannot be reused. This is known as the “3R” rule, an initiative that started in Japan in 2002 and advocated by the G8 Summit in June 2004, to globally promote a society that recycles and uses resources and materials efficiently.

Landfill has been the traditional method for treating waste that was technically impossible to recycle but the problem is that they make an unsustainable use of land and pose environmental concerns including water and air quality issues. Consequently, it has been necessary to develop new technologies in order to prevent these negative impacts: The energy recovery plants, also known as “Waste to Energy” plants or W2E.

Lara: W2E is the answer

Lara: W2E is the answer

The energy plant works by burning waste at high temperatures and using the heat to make steam. The steam then drives a turbine that creates electricity. W2E is one of the most robust and effective alternative energy options to reduce CO2 emissions and replace fossil fuels. Approximately 2/3 of household waste is categorised as biomass. Therefore, we can recover 2/3 as CO2-neutral energy and reduce our dependence on fossil fuels.

Within this entire context, our UAE leaders are working now on this technology and Masdar, Abu Dhabi’s renewable energy company, had signed a strategic partnership agreement with Sharjah´s Bee’ah to develop the UAE’s W2E sector. This partnership will help contribute to the UAE Government’s Vision 2021, which targets, among other goals, diverting waste from landfills by 75 per cent by 2021. Dubai has awarded the largest W2E in the world and the rest of the Emirates are swiftly developing similar plans for the coming years.

 

HOW DOES A W2E PLANT WORK?

W2E plants comprise a series of facilities with specific functions in order to convert waste into energy via a multi-stage process:

• The waste arrives at the reception and storage zone where it is weighed, unloaded and stored. Since the plants operate 24 hours a day throughout the year, sufficient waste must be stored to ensure uninterrupted operations at all times.

• Another facility, which is typical within an energy recovery plant, is the mechanical waste classification zone, where waste is classified by size, density or type of material.

• Plants that receive a significant amount of organic waste also have a biological treatment zone. Two types of processes are generally used: composting to produce compost (organic fertiliser) and anaerobic digestion, which produces a biogas that can be used for electricity or can be washed to produce natural gas.

The W2E plant in La Rioja Ecopark (Spain): producing energy from urban waste

The W2E plant in La Rioja Ecopark (Spain): producing energy from urban waste

• The waste is burnt in combustion furnaces at temperatures in excess of 850-deg C in order to prevent dioxins forming. The by-product of this combustion is slag, which can be used as a construction material.

• The heat produced by the furnaces is converted into steam in the boilers, which are especially designed to collect the ash generated by the combustion.

• The steam drives the turbines to produce electricity or heat.

• Flue gas Treatment. Emissions to air are critically controlled in these facilities, as they are required to comply with the most stringent emission levels in the industry.

 

ENERGY RECOVERY

Producing energy from urban waste is not an alternative to recycling, but is a complementary process in the search for increasingly sustainable environments.

The W2E plant in La Rioja Ecopark (Spain) was built by Acciona as a benchmark for Urban Solid Waste Mechanical Biological Treatment facilities

The W2E plant in La Rioja Ecopark (Spain) was built by Acciona as a benchmark for Urban Solid Waste Mechanical Biological Treatment facilities

In short, it is a way of preventing landfill. Moreover, these new facilities offer major advantages compared to traditional methods of treating waste. Firstly, they use proven and wholly reliable processes. Secondly, the waste that they process requires very little prior treatment since the systems are extremely robust and flexible. This aspect is extremely useful considering that the types of waste generated by a population can change significantly over the life of these plants (around 30 years).

Compared to landfills, which generate very little usable material, the waste to energy process recovers electricity and heat doing this with extremely strict emissions controls. W2E plants also offer other environmental advantages compared to landfills: recovering energy from waste saves on fossil fuels such as coal, gas and oil. Furthermore, in general, they do not produce liquids that could filter into the subsoil. Instead, they produce by products such as metals and slags that can be recovered and recycled.

The unquestionable benefits of energy recovery processes based on urban waste have led to the regional expansion of this approach: the Abu Dhabi National Energy Company (Taqa), developed a facility near the sea port in Mussaffah that has an annual capacity of 1 million tonne of solid waste which can be converted into 100 MW of energy, sufficient to power around 20,000 Abu Dhabi homes. It is expected to reduce CO2 emissions by more than 1 million tonne per year. Besides, by the second quarter of 2020, Dubai will have the largest plant in the Middle East to convert W2E. The project is in line with Dubai Municipality’s vision to make the city the most sustainable and smart city by 2021. The UAE aims to be one of the leading countries in the GCC to achieve the highest rate of solid W2E management while also reducing the number of landfill waste by 75 per cent by 2021.

The most significant challenge to WTE technology adoption is the awareness that waste can be used as a source of clean and reliable energy. In Acciona, we are highly committed to contribute to sustainable development in the industrial sector and we are focusing our strategy on working towards clean and competitive technologies all over the world and the GCC region. Last year for example, Acciona started to build Australia’s first large-scale thermal Waste to Energy plant at Kwinana (Perth).

Our R&D+i team together with the Acciona Infrastructure Technology Centre and the corporate innovation team, are working on new processes and technologies that have the potential to offer superior performances in order to be even more environmentally-friendly: hybrid W2E Thermosolar plants or gasification processes that obtain chemicals from the syngas-synthesis gas, among others. Therefore, we have the necessary capacity and experience as well as core values that include a commitment to sustainable and environmentally friendly procedures.




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