Ōtautahi Christchurch organics processing facility

The Council has approved Ecogas(external link) as the new long-term organics processor, following a multi-stage procurement process.

A 100% New Zealand partnership between Pioneer Energy and EcoStock, Ecogas currently operates an anaerobic digestion plant in the North Island. Ecogas has experience with managing organic waste with two existing North Island sites (Papakura Auckland and Reporoa).

This new plant will be fully enclosed, in an area zoned for this type of work. 

Unlike the plant at Bromley, it won’t do composting, and no waste will be kept outside. It’s a proven process that Ecogas is already running in the North Island, with no negative impacts on their neighbours. This technology is already used successfully in cities around the world, including London, Sydney and Madrid. 

The new organics processing plant will allow for a fully enclosed process, which uses anaerobic digestion technology and a biofuel processing line to convert mixed kerbside organics and garden waste into fertiliser, biogas, and biofuel.

The biogas produced through the anaerobic digestion process will be used as a renewable energy alternative to current fossil fuels. The liquid portion becomes a biofertiliser, used to regenerate soil and provide nutrition for crops.

You can find more answers at Ecogas.(external link)

The process

How does anaerobic digestion work?

Anaerobic Digestion (AD) is a natural process where microorganisms break down organic waste such as food scraps in a sealed system, without oxygen. This produces valuable resources in the form of energy (heat, gas and used to generate electricity) and digestate.

Digestate is a nutrient-rich substance which is used as fertiliser that actively regenerates soil health and replenishes carbon.

How does anaerobic digestion compare to composting?

Composting and Anaerobic Digestion (AD) are great complementary tools for different jobs. Most importantly, they both keep waste out of landfills. Both composting and AD preserve nutrients contained in the original feedstock and recycle them back into the soil.

Composting is best suited for primarily drier and bulky green waste and plant materials.

Organic waste that is full of fats, oils or protein is better processed through anaerobic digestion. Food waste is typically high in water content, which is processed well using AD.

What by-products does the process create?

Anaerobic Digestion results in two products: energy (gas, heat and generating electricity) and digestate.

Liquid digestate is used as fertiliser on local farmland while biogas is used to generate electricity to power our plant and be converted as a renewable substitute for natural gas.

What is biofuel?

Biofuel is a fuel that is produced from biomass rather than by the very slow natural processes involved in the formation of fossil fuels.

The Ōtautahi Christchurch Regional Organics Processing Facility will produce biofuel in the form of biogas from the digestion process and includes a process to convert the more woody and fibrous materials into biofuel in the form of a wood chip. The ‘chip’ can then be burned to produce energy as a replacement for fossil fuels.

Does the new facility take the same organic waste as the Organics Processing Plant in Bromley?  Will it be processing dairy farm effluent?

The kerbside green bin waste (food and garden organics) and garden waste from the transfer stations are the same as what’s currently going to the Organics Processing Plant in Bromley. The Ecogas facility will also take industrial organic waste including dairy (factory) waste. Dairy effluent from farms will not be processed at this facility.

Odour and environmental impacts

Will the new facility produce any odour?

Ecogas is confident that the design of the facility along with the processes for handling the organic material will manage any odour. Ecogas has experience with managing organic waste, having successfully managed odour at its existing North Island sites.

The new facility will be enclosed with no outside storage or processing of materials. The design will feature technology such as a biofilter and rapid close doors. The kerbside food waste will be processed quickly on arrival, with contamination removed before it is pumped into the fully sealed anaerobic digestion tanks.

The green waste will be chipped and dried inside before quick dispatch to energy customers. The fast, enclosed processing of the waste will prevent any odour issues.

How will the facility stop odours from moving to neighbouring areas?

We do not anticipate any odour issue for any of the surrounding areas. The building design is tailored for each individual site and operates under negative pressure. This means air is sucked into the building, stopping the odour from being released. All exhaust air is treated before release to remove odours.

The new facility will be enclosed with no outside storage or processing of materials. The design will feature technology such as a biofilter and rapid close doors. The kerbside food waste will be processed quickly on arrival, with contamination removed before it is pumped into the fully sealed anaerobic digestion tanks.

The rapid close doors, combined with negative air pressure, are designed to stop the wind from affecting odour.

What environmental impacts are there?

Ecogas sites are self-sufficient in energy, producing enough to power the plant. The facilities produce minimal emissions due to the capture of gas during the anaerobic digestion process. The facility is fully enclosed which means there is no outdoor processing or storage of products.

Where possible, Ecogas uses backhaul loads (where trucks would otherwise return empty) to transport organic waste. This minimises transport emissions and reduces traffic impacts.

Anaerobic digestion produces biogas which when combusted in boilers or engines, is turned into carbon dioxide. As the biogas is biogenic (from recent plant growth as opposed to a fossilised source such as coal), this CO2 is considered neutral from a greenhouse gas (GHG) perspective.

The liquid residue from the AD process, digestate, replaces synthetic fertilisers on farms, and reduces reliance on imported materials with a high carbon footprint.

The wood portion from the biofuel line is used as a renewable energy alternative to current fossil fuels.

Overall, anaerobic digestion and biofuel production has a net positive impact on the environment, by diverting organics from landfill and providing renewable, alternative energy sources.

How much water is used in anaerobic digestion?

The Ecogas facilities are designed to be “closed loop” systems. Dry and wet waste will be mixed to avoid adding any water for dilution. Rainwater is used for process requirements and all washdown water is recycled back into the process to ensure no liquid is discharged into the environment.

Why is digestate from an AD plant more climate-friendly than synthetic fertilisers?

Anaerobic digestion of food waste produces a liquid residue called digestate which can be applied to land as a nutrient-rich fertiliser. Synthetic fertilisers are manufactured using energy-intensive processes that rely on fossil fuels.

Biofertilisers such as anaerobic digestate can help to displace the demand for synthetic fertilisers by providing nutrients from organic waste streams in fertiliser form. Digestate consequently reduces our reliance on fossil fuels, the need to transport these fertilisers worldwide, and all the emissions incurred from this supply chain.

Additionally, the digestate produced by Ecogas, Fertify™, has a high carbon content which is valued in regenerative farming practices for promoting healthy soils.

What will the impact be on the local environment?

There will be minimal impact on the environment. Ecogas has experience with managing organic waste with two existing North Island sites (Papakura Auckland and Reporoa).

Ecogas facilities produce minimal emissions due to the capture and beneficial use of the gas generated during the anaerobic digestion process. The facility is fully enclosed which means there is no outdoor processing or storage of products.

The facility will deliver a different system from how things are done at the existing Organics Processing Plant at Metro Place in Bromley. The new solution provides an industry-standard, sustainable practice for organics processing, servicing both our growing city and region.

Ecogas is confident that the design of the facility along with the processes for handling the organic material will prevent any odour from being released.

The new facility will be enclosed with no outside storage or processing of materials. The design will feature technology such as a biofilter and rapid close doors. The kerbside food waste will be offloaded inside the fully enclosed reception hall where it is processed quickly, with contamination removed before it is pumped into the fully sealed anaerobic digestion tanks.

The green waste will be chipped and dried inside before quick dispatch to energy customers. The fast, enclosed processing of the waste will prevent any odour issues.

Operations and development

When will the Ōtautahi Christchurch Regional Organics Processing Facility be operational?

The Christchurch Organics Processing Facility will start taking kerbside organics in late 2026.

How long is the Ecogas contract for?

Twenty years.

How much will the organics processing facility cost?

Ecogas is investing in the plant and the Hornby community. The Council’s contribution is in the form of a gate fee for processing organic material. This is expected to be covered within planned budgets. At this stage, this remains commercially confidential.

Where will the plant be located?

It will be located at Aruhe Road, South Hornby, in an area zoned for heavy industrial activity. The facility will be designed to minimise impacts on neighbouring businesses and the environment.

How big will the facility be compared to the Ecogas facilities in the North Island?

About twice the size. The Christchurch facility covers three hectares and includes additional space needed for the biofuel processing operation so has a bigger building footprint than the Reporoa facility. In comparison, the footprint of the Organics Processing Plant in Bromley is more than nine hectares.

Why was there no consultation with the community about the long-term kerbside organics processing solution?

The project to find a solution to process kerbside organics was consulted on in a previous annual plan process.

The Council does not consult on procurement processes as these are commercially sensitive and must be undertaken in confidence. For the procurement of the long-term solution for processing kerbside organics, in June 2022 the Council’s Finance & Performance Committee approved the first stage of the procurement plan, an Expression of Interest (EOI) to shortlist viable solutions, and to report back to the Council.

In March 2023, the Council approved the second stage of the procurement plan – which was a request for proposals (RFP) from the six shortlisted EOI respondents. This was done on the basis that these proposals provide a complete solution for processing kerbside organics (site, technology, operator, and markets for products).

They must also demonstrate alignment with the Council’s objectives for processing kerbside organics.

Why was the location of the new facility in South Hornby not consulted on?

The new facility is not Council-owned and the land it will be built on is owned by Pioneer Energy, Ecogas' majority shareholder. This means it goes through the usual planning processes (building and resource consent), and not a Council-led consultation process.

Will there be a lot of trucks coming and going?

Traffic impacts have been carefully considered and minimised. Where possible, Ecogas uses backhaul loads (where trucks would otherwise return empty) to transport organic waste. This minimises transport emissions and reduces traffic impacts.

The facility is designed to unload trucks with a maximum turnaround time of 15 minutes. This specification is based on the Council’s kerbside truck delivery model that currently runs at the Organics Processing Plant in Bromley. We do not anticipate there will be a queue of trucks waiting to unload.

Will there be a double-door airlock for trucks coming in and out of the facility?

The facility design will not have airlocks for the truck movements as they are not effective enough to contain odour. The new facility will use up-to-date technology such as auto control rapid close doors and negative air pressure to contain any odour. The doors will automatically open and close, and the facility will run at negative pressure which means air is sucked into the building and odours stay inside. All air leaving the building passes through a biofilter to clean it before it is released.

Will the trucks carrying food waste be fully enclosed?

Yes, these are the existing kerbside collection trucks and any industrial organics from other sources will be in fully sealed trucks e.g. tankers.

Is this a 24/7 operation?

No, it is planned that the facility generally operates from 6am to 6pm Monday to Friday. There may be after hours or weekend activities to cater for situations such as public holidays.

Why did Ecogas choose the South Hornby site?

The site location has been determined by Ecogas and has been selected based on several factors including proximity to existing arterial traffic routes, minimisation of impact to the existing kerbside collection, zoning, adjacent industrial neighbours, and planning advice.

The new facility in South Hornby will not be Council-owned, and the land it will be built on is owned by Pioneer Energy, Ecogas' majority shareholder. The site is in an area zoned for heavy industrial activity. The site has been chosen with careful consideration of environmental and amenity impacts, and the facility will be designed to minimise impacts on neighbouring businesses and the environment.

What will the impact be on the local environment?

There will be minimal impact on the environment. Ecogas has experience with managing organic waste with two existing North Island sites (Papakura Auckland and Reporoa).

Ecogas facilities produce minimal emissions due to the capture and beneficial use of the gas generated during the anaerobic digestion process. The facility is fully enclosed which means there is no outdoor processing or storage of products.

The facility will deliver a different system from how things are done at the existing Organics Processing Plant at Metro Place in Bromley. The new solution provides an industry-standard, sustainable practice for organics processing, servicing both our growing city and region.

Ecogas is confident that the design of the facility along with the processes for handling the organic material will prevent any odour from being released.

The new facility will be enclosed with no outside storage or processing of materials. The design will feature technology such as a biofilter and rapid close doors. The kerbside food waste will be offloaded inside the fully enclosed reception hall where it is processed quickly, with contamination removed before it is pumped into the fully sealed anaerobic digestion tanks.

The green waste will be chipped and dried inside before quick dispatch to energy customers. The fast, enclosed processing of the waste will prevent any odour issues.

Will there be an outside water storage pond?

No, this is one of Ecogas’ learnings from its North Island sites. Stormwater on the Hornby site will be stored in a tank.

When will the resource consents for the new facility be lodged and processed?

The new Ōtautahi Christchurch Organics Processing Facility will be privately owned and operated by Ecogas, which has made the decision to build its commercial facility on land in South Hornby in an area zoned for heavy industrial activity.

In October 2024 Christchurch City Council granted land use consent for the EcoGas Organics Processing Facility at 17-21 Aruhe Road (reference number RMA/2024/2050(external link)).

The proposal is also contingent on a resource consent from Environment Canterbury (reference number CRC250284)(external link).  Questions about the Environment Canterbury resource consent process should be directed to Environment Canterbury to answer.

Where do we go for more information?

Email your questions to organics@ccc.govt.nz.