Exploring potential benefits of biodigester technologies

Date released

14 December 2023

Biodigesters exemplify a classic challenge of the circular food economy: how do we bring together the diverse actors in the food and agriculture system to coordinate investment, adoption and impact that considers the local context?

Diverse benefits

Biodigesters, through anaerobic digestion, help manage waste in the environment. By breaking down organic matter in a closed, controlled system, they can reduce the associated greenhouse gases produced by waste decomposing in open environments. That waste can be food scraps, crop residues, animal manure or human waste.

By removing manure and organic waste from farms, biodigesters can reduce the risk of pathogens such as leptospirosis spreading in soil and water, and affecting animal and human health.

The waste digestion process produces methane, which can be captured and used as a renewable source of energy to power home cooking and lighting systems. It is an alternative to wood and fossil fuels such as LPG, diesel and kerosene, and can help reduce household energy costs.

And after the organic matter has been broken down, the remaining material, called digestate (both liquid and solid material), can provide a nutrient-rich organic fertiliser to build soils and improve agricultural production.

This, in turn, improves livelihoods for households and smallholder farmers. It supports sustainable agriculture and food security for Fiji’s growing population.

outdoors, trees, a small area fences a large black, airtight, high-density polyethylene container. — Biodigesters, through anaerobic digestion, help manage waste in the environment.

Coordinated approach

ACIAR Research Program Manager, Climate Change, Dr Veronica Doerr said the technology had the ability to contribute to many of Fiji’s national goals, including its commitment to a low-carbon, low-emissions economy.

However, the responsibility for and interest in different benefits – for waste management, climate and the environment, health, energy and agriculture – was fragmented across different sectors.

‘As a result, it’s not a top priority for anyone, in terms of funding technical research or driving adoption,’ noted Dr Doerr. ‘Each sector might make a small investment, as they have funds available, that reflects their own priorities.

‘But if you could sum all those benefits, and bring all those potential contributions together with everyone playing complementary roles, you end up with a really large benefit, a strategic investment and widespread adoption of the technology.’

The potential for a coordinated effort to make a significant impact underpins an ACIAR-supported scoping study underway with partners in Fiji to look at the roles of different actors – government, private sector and international development agencies – in promoting biodigester technology and its benefits.

Adoption challenges

Leading the scoping study is food systems and social scientist, Dr Federico Dávila, from the Institute for Sustainable Futures at the University of Technology Sydney.

He said waste management and energy tend to be the primary focus when biodigesters are installed. However, the scoping study will determine the potential value of all co-benefits, including climate benefits. It will also identify strategies to establish governance models to maximise those co-benefits.

Biodigesters operating in Fiji have been funded by government, international development agencies, or privately by individual families.

‘While we are expanding our view of the benefits to agriculture, we’re also looking at what’s enabling either public or private investment, to support long-term adoption in the Pacific,’ said Dr Dávila.

‘Part of our review has been looking at previous biodigester trials in the Pacific.

‘We are interviewing farmers about their experiences, the benefits and challenges, to understand how to address the underlying factors that determine long-term success of biodigester systems.

‘There are lessons to be learned from the challenges of maintenance and enabling the users to understand the systems and maximise their benefits. And a lot of that revolves around learning and capacity-building questions.’

Dr Dávila said the scoping study would help develop a larger project looking at a governance structure for circular agri-food-energy systems (biodigesters) and climate co-benefits in Fiji.

Project partners with ACIAR and the University of Technology Sydney include Pacific Grow, Wildlife Conservation Society and Eco-Grow Fiji.

a group of 4 men outdoors looking down at growing plants. — Project partners with eggplants grown with biodigester fertiliser output. Photo: Dr Federico Dávila

Local knowledge and impact

Mr Mesake Cataki is the founder of Eco-Grow Fiji, a home biogas system supplier who is providing technical support and local knowledge about farmer challenges for the scoping study.

He said the systems-based approach of the ACIAR-supported study could provide a potential trigger for a transformative mind shift in the way the country perceives waste, elevating it as ‘a crucial element that yields renewable energy and enriching resources’.

‘It is also timely, given the multitude of challenges facing Fiji and the broader Pacific region, including the intensifying impacts of climate change, non-communicable diseases, nutritional food shortages
and inflation,’ said Mr Cataki.

‘Smallholder farmers have been severely affected by the rising cost of fertiliser, drastic changes in weather patterns and declining soil health. Making more of waste is a matter of utmost importance in our pursuit of sustainability and resourcefulness.

‘It is important for Fiji to see waste as a resource, a vital input that is upcycled into the economy. It is available locally and, if used effectively, can help us to protect our biodiversity, build our economy, make us more independent and resilient.’

ACIAR PROJECT: ‘Scoping the governance and co-benefits of circular food-energy systems in Pacific Islands Countries’ (CLIM/2022/174)