Published by Recycling & Waste World

It could be argued that of all the resources waste managers manage, bio-resources are the most critical to ‘get right’.

Biowaste managers play an important role in supporting the nutrient cycle, converting food waste into fertiliser and returning it to the land. 2015 was the International Year of Soils, and if we learned one thing, it was the profound importance of soils to human life. Closing the nutrient loop from field to fork and back again is an investment in the future of humanity.

Using compost or digestate instead of chemical fertilisers has proven benefits, with its slow-release of nitrogen, phosphorous and organic carbon matter, as well as improved water retention (hence in some north African countries compost sells at €300/tonne).

Meanwhile in terms of climate change, biowaste management is seen by some as the next frontier. With decent waste management lagging behind rapid urbanisation in developing countries, methane emissions continue to rise while soils become increasingly depleted.

Dr Marco Ricci Jürgensen, Chairman of the Working Group on Biological Treatment of Waste at ISWA International Solid Waste Association, said: “We need to better understand the global impact of compost and digestate on soil carbon sequestration. A strong evidence base on biowaste and climate change is needed to guide policy on the management of food waste from cities.”

The ISWA Working Group on Biological Treatment is planning a Key Issue Paper on this very subject, and its outcomes are likely to influence actions towards achieving certain Global Goals (Sustainable Cities, Affordable and Clean Energy, Climate Action, Life on Land).

The risks of contamination

Keeping the nutrient cycle ‘healthy’ means keeping contamination to a minimum.

Soil contaminants (such as POPs and heavy metals) are absorbed by crops and livestock, with devastating effects on human health and the natural world. Persistent contaminants make their way into the groundwater that people drink and irrigate their crops with, and ultimately end up in surface waters.

Ricci Jürgensen continued: “The European Commission carried out a detailed study to assess background concentrations of pollutants in organic fertilisers and soil amendments. It drew a clear conclusion that the potential concentrations of toxic elements in compost produced from separately collected organic household waste decreased by a factor 2 to 10 as compared to MSW compost or to stabilised organic waste fraction from MBT.

“This information has guided the development of European legislation around composting, including the final draft of the End-of-Waste legislation that demands source-separated (non-contaminated) feedstock for the production of quality compost.”

Speaking at the International conference on Sustainable Food and Bio Waste Management in Malta earlier this year, the Commissioner for Environment, Maritime Affairs and Fisheries, Karmenu Vella said: “We are looking to manage biowaste more effectively. A lot of biowaste, quite simply, is the result of wasted food. It often makes up half of all municipal waste and it poses considerable environmental risks.

“That’s why the Commission has proposed separate collection of bio-waste. It will improve recycling generally, and it will also close a loop, when biowaste goes back to soils in the form of compost and fertiliser.”

A global, urbanised, perspective

The way that biowaste is collected varies from town to town and indeed country to country. Even within the EU there are dozens of systems of collecting and treating biowaste, each with their strengths and weaknesses when it comes to cutting down on contaminants.

Cost is always a critical factor and low-cost biogas production and mini-grids offer interesting potential in this regard. Different financing mechanisms have been explored, with the much-cited CDM municipal waste composting programme in Uganda being the first to be funded via revenues generated from the sale of both compost and carbon credits. However, while a popular model for some years, experience has shown that financial sustainability needs to rest beyond the global carbon credit market.

Importantly, the proportion of biowaste in household waste decreases with average household income. In developing countries the percentage of biowaste in MSW can be up to 85%, compared to <20% in the wealthiest countries. Countries with high levels of biowaste need to establish low-cost and easily replicable collection and treatment systems along with community-based education and training.

Managing organic waste streams is one of the critical challenges facing rapidly urbanising areas. In addition to food waste, the amount of sludge that must be properly disposed of increases with added capacity in waste water treatment.

Tom Frankiewicz, from the U.S. Environmental Protection Agency described their approach taken through the Global Methane Initiative in China, “We target rapidly growing second-tier cities to establish a baseline of organic waste treatment and recommend specific activities to implement to improve waste management, reduce methane emissions, and improve air quality.”

“While cities may be most interested in improving waste management, it is also critical that we help them establish the linkages between climate, public health, and nutrient managment.”

It is surely through making such links that the true business case for biowaste management can be established. The newly released Food Waste Composting Action Plan for England (WRAP) set out a valuable five point plan for developing robust systems:

  1. Developing the business case
  2. Optimising food waste collections
  3. Communicating with householders and commercial food waste producers
  4. Ensuring quality as well as quantity
  5. Making contracts work.

Those considering setting up a municipal composting scheme would do well to learn from others’ (sometimes costly) experiences. Different examples of good practice are emerging across the globe, as researchers and practitioners develop and refine systems that work in different cultures, geographies and budgets.

The forthcoming ISWA congress will showcase this diversity, with case studies on home composting in Serbia, centralised composting in Uganda and MBT in Tunisia, a coffee waste biodigester built with ecobricks in Colombia and the stabilisation of dredged sludge at a theme park in Istanbul. Two key sessions on biowaste treatment and management are planned, chaired by Dr Marco Ricci Jürgensen and Dr Jane Gilbert, both members of the European Compost Network.

The ISWA congress brings together waste managers, municipal authorities, policy makers and academics and is the only global event of its kind. ISWA 2016 takes place in Novi Sad from 19-21 September. For more information visit