Hybrid composting systems: appropriate technology for Austral-Asia?
Composting is a strongly emerging option in waste management in Austral-asia. It has been widely acknowledged that a successful integrated waste management strategy must adequately address the organic waste stream. Composting is the most economical, efficient and ecologically sustainable option to deal with organic waste if properly managed and economically and socially integrated into a management system.
Full integration must include long term economically, socially and environmentally sustainable applications and markets for the final product. This means that compost must be of sufficiently high quality not to pose public health, environmental or nuisance problems when handled or applied to land. In order to achieve this integration composting requires a systems approach in which the following parameters are relevant:
Quality control of raw materials that form the substrate;
Appropriate composting technology, and
Stringent control on compost quality to meet long term marketing and environmental and public health objectives.
The recently adopted Standard for Compost, Mulches and other Soil Conditioners (Standards Australia, 1997), and the development of guidelines for the reuse of biosolids by the agricultural resource management council of Australia and New Zealand (ARMCANZ, 1995) are evidence of the recognition of the National objectives to achieve sustainable organic waste management practices.
The current interest shown in composting as a waste management option can not be taken for granted by government authorities and the waste management industry. The industry has in the past suffered many examples of failed attempts at integration of composting into waste management. Inadequate quality control of both raw input materials and final compost product, as well as application of inappropriate technology and management practices, causing system failure due to significant environmental and health impact, and lack of sustainable compost markets, resulting eventually in rejection of the option on social and economic grounds. Potential impacts of inappropriate technology can include: vermin and insect (flies, mosquitoes) breeding; odour emission; leachate generation; compost contamination (pathogens, metals, inorganic particles, etc.) and immature compost.
Each compost plant operator inadvertently has a responsibility to contribute to the long term sustainability of the wider composting industry, as each failure may contribute to the rejection of the concept as composting as a component of an integrated waste management system.
Though quality control on the materials flow increasingly receives an appropriate level of attention, the criteria for composting technology that is appropriate to local conditions and the assessment of existing technologies has not.
Some of the relevant criteria for appropriate composting technology include:
- Production cost per unit product;
- Level of technology, in terms of complexity and mechanisation;
- Environmental & health impact;
- Land and zoning requirements;
- Compost quality in terms of meeting quality standards and matching market requirements;
- Level of transparency and acceptance to the community.
In this paper the main composting approaches are described and includes the description and assessment of an innovation, the hybrid composting system.