Turning waste into energy

With the world's focus on the environment during COP 17, Joburg scientists and engineers have announced ground-breaking technology that deals with waste, and generates fuel.
NEW ground has been broken with technology that converts agricultural and municipal waste into fuel, electricity and paraffin.

The waste unit container turns waste into fuelBeauTi-fuel converts waste into fuelDeveloped by an engineering team from Wits University’s Centre of Material and Process Synthesis (Comps) and scientists at the Nuclear Energy Corporation of South Africa (Necsa), the project has been hailed a “sustainable and small-scale solution to waste management”.

Wits has invested about R5-million in piloting the project, which will be exhibited at the United Nations Framework Convention on Climate Change’s 17th Conference of the Parties (COP 17) in Durban, which began on 28 November. It is to run until 9 December.

According to Vivienne Rowland, a Wits spokesperson, a fully fledged prototype of the technology will be constructed next year and displayed at various public events and locations around the country.

“During this period, the technology will be refined and the facility will be demonstrated to potential clients,” she says. “It is the first time that this innovative project developed in South Africa by South Africans has been manufactured on a small scale to make it economical for South Africa and other developing countries.”

Fuel
Called BeauTi-fueL, the technology is able to convert one ton of biomass into one barrel of diesel and 0.5MWh of electricity per day, says Prof Diane Hildebrandt, the co-director of Comps, which is in the Wits School of Chemical and Metallurgical Engineering.

Converting biomass into fuel needs a combination of technologies, including a plasma gasification unit developed by Necsa and a Fischer-Tropsch unit developed by Comps.

Through BeauTi-fueL, biomass is converted into syngas in a plasma gasifier. The syngas is then cleaned to reduce harmful contaminants that may damage the reactor system. The clean syngas is then processed to a reactor that contains Fischer-Tropsch catalysts. The product stream from the reactor is then cooled and product cuts removed. The remaining tail gas is passed to an electricity generation unit.

“The process is flexible and the ratio of fuel-to-electricity production can be varied accordingly,” says Dr Michaela Very, the Comps director.

Jobs
Hildebrandt says that through this innovation, her department aims to create about 200 jobs for unskilled labourers, address issues of waste management, and reduce greenhouse gas emissions.

“It is intended that when implemented, this economical project will have a very strong job creation aspect in terms of growing the agricultural material, collecting and sorting municipal solid waste and supplying fuel and electricity to small municipalities, rural areas and small farming areas,” she explains.

Rowland says a full-scale BeauTi-fueL plant would treat 91 000 tons of municipal waste yearly, enough to generate electricity for 10 000 homes. The project, which has a neutral carbon footprint and minimal environmental impact, will also increase recycling rates by over 20 percent.

“In the long run we would hope to use the very clean carbon dioxide produced by the process to grow algae that could be harvested and fed back to the plant or used to feed fish. This will be labour intensive and could create even more work for unskilled people, as well as possibly providing protein from the fish for consumption purposes,” Hildebrandt explains.

It is expected that once fully operational, the project will have commercial value. The proposal is to build small modular processes that have the advantage of being less capital intensive, more flexible and a faster time-to-market, Very says.
“The capacity of the process would depend on feedstock availability and transportation,” Very adds.

“The superior conversion efficiency of the plasma gasifier and the ease with which the process gas could be manipulated to optimise the fuel production, combined with the resultant fuel gas generating electricity, renders this a sought-after system for anyone who generates waste,” says Dr Jaco van der Walt, a plasma scientist at Necsa.

Landfill
In addition, the City of Joburg has invested more than R200-million in developing a similar project, which uses gas turbines to drill out methane gas caused by the degradation of bio-organic compounds at its landfill sites, to generate renewable energy for the municipal grid.

The initiative, Landfill Gas to Energy Clean Development Mechanism Project, is expected to be fully operational by 2012. The use of methane-rich gas to generate renewable energy is now a global trend and is considered a commercially viable, cost-effective technique.

An estimated 17MW of power will be generated from the project, comparable to electricity use of about 13 000kWh to 14 000kWh in middle income households each year. This will be sustainable for 15 to 20 years, though the rate of gas production is dependent on the age and composition of the waste, the temperature and moisture content of each site, and the design and operation of the site.

Joburg’s project supports South Africa’s commitment to the Kyoto Protocol, an international agreement linked to the United Nations Framework Convention on Climate Change that aims to reduce greenhouse gas emissions for a carbon neutral planet.