Department of the Environment, Water, Heritage and the Arts Waste Technology and Innovation Study

Download 6.17 Mb.
Size6.17 Mb.
1   ...   56   57   58   59   60   61   62   63   ...   129

Waste to Biofuel

At the pilot/testing stage is a bioreactor process that uses microorganisms to create ethanol from waste developed by US-based Coskata Inc which in 2008 entered into a program with General Motors to develop the fuel on test vehicles.48
      1. Microwave Technology

New Zealand company Carbonscape uses industrial microwave technology to convert wood and other biomass to biochar. Each industrial microwave unit converts 40–50% of wood debris into charcoal, which can be added to soils.
      1. Bioreactor Landfills49

A bioreactor landfill is a conventional sanitary landfill that uses enhanced microbiological processes to transform and stabilise the readily and moderately decomposable organic waste constituents more quickly than a conventional landfill. The most significant element of a bioreactor landfill is the addition and recirculation of water (as leachate) through the accumulated waste. Other management strategies include waste shredding, pH adjustment, nutrient addition and temperature management. This process speeds up microbiological activity, hence waste decomposition, and gas generation providing the advantages of a significantly shorter decomposition process, rapid settlement and stabilisation of the site, better leachate processing and control and better energy recovery through gas capture.

There are three types of bioreactor landfills:

  • Aerobic - leachate is removed from the bottom layer, piped to storage tanks, and re-circulated into the landfill in a controlled manner. Air is injected into the waste mass, using vertical or horizontal wells, to promote aerobic activity and accelerate waste stabilisation;

  • Anaerobic - moisture is added to the waste mass in the form of re-circulated leachate and other sources to obtain optimal moisture levels. Biodegradation occurs in the absence of oxygen (anaerobically) and primarily methane, can be captured to minimise greenhouse gas emissions and for energy projects; and

  • Hybrid (Aerobic-Anaerobic) - employing a sequential aerobic-anaerobic treatment to rapidly degrade organics in the upper sections of the landfill and collect gas from lower sections. Operation as a hybrid results in the earlier onset of methanogenesis compared to aerobic landfill.

Because the nature and density of the waste is a critical element in the management and success of a bioreactor landfill, it is not a technology that is easily applied to existing landfills. The way waste has been deposited at existing landfills does not normally allow water to contact and move uniformly through it. As a result injection and drainage systems become fouled and large volume of leachate are required for flushing. This in turn requires treatment and disposal.

Bioreactor landfills do not recover or recycle any materials but the accelerated biological activity produces a greater quantity of gas more quickly which can be used for electricity generation. There are two bioreactor landfills in Queensland, the Ti Tree facility operated by Veolia, and the Swanbank facility operated by Thiess, and one in NSW, the Woodlawn Facility near Goulburn operated by Veolia.

      1. Share with your friends:
1   ...   56   57   58   59   60   61   62   63   ...   129

The database is protected by copyright © 2020
send message

    Main page