The impact of the Green Machine on food waste emissions

EAS were approached by the innovative Green Machine to assist in understanding how their product could help businesses reduce food waste, decrease their carbon footprint, and save money. As avid supporters of innovative solutions that encourage businesses to reduce their greenhouse gas footprint, we were eager to assist.

If your business or organisation deals with food waste, then the following case study may be of interest.

1.1 The Food Waste Problem

Annually, it is estimated that up to 968,000 tonnes of commercial and household food waste are discarded in New Zealand, with the majority ending up in landfills. This process results in the anaerobic decomposition of waste, producing methane, which is a potent source of greenhouse gas emissions.

1.2 What is the Green Machine?

The Green Machine is a food waste processor that aims to reduce the greenhouse gas emissions caused by food waste by creating an easily compostable end-product as an alternative to landfill disposal. The processor grinds food waste into smaller particles and separates the macerated solids from excess liquid. This method reduces the solid waste to roughly 20% of its original volume, with the remaining 80% forming a liquid waste stream that can be sent down the drain. The final solid food pulp is perfectly suited for downstream composting.

The reduction in waste volume translates to an 80% decrease in storage, collection, and transport requirements. For example, instead of sending 10 wheelie bins of food waste to the landfill every week, the waste truck now only needs to transport and empty two wheelie bins. As composting sites become more accessible on a local scale, transportation and distribution emissions will be further reduced in comparison to traveling long distances to national landfill sites.

The Green Machine Food Waste Processor (Image Source

The Green Machine also promotes the adoption of a Bokashi composting system, which utilises an organic culture to ferment the food pulp anaerobically into a natural soil conditioner. This composting method produces nutrient-rich compost and a liquid waste stream that can be used as fertiliser, with the potential to offset greenhouse gas emissions related to artificial fertiliser production and use. The Bokashi composting process ferments organic waste anaerobically at a low pH, significantly reducing greenhouse gas production since methane-producing microbes cannot survive at a low pH. However, more research is necessary to fully understand the impact on methane, carbon dioxide, and nitrogen dioxide when placed in the soil.

Implementing a Green Machine in conjunction with a composting system can mitigate greenhouse gas emissions by diverting waste from landfills, decreasing emissions by approximately 0.3 tCO2e per tonne of waste.

2    Case Study Boundary

The scenario presented here is based on an average café in Wanaka that produces 17.85 tonnes of food waste per year. The aim of this case study is to provide a comparison of greenhouse gas emissions in the typical business-as-usual situation where food waste is sent to landfill (Scenario 1) against a situation where a Green Machine and Bokashi composting system is implemented (Scenario 2). [N1] . The activities included within the boundary of this case study were therefore limited to those that would be affected by this change in operation, as summarised in Table 1.

Table 1: Activities included in boundary

ActivityScopeIncluded or Excluded
Direct Emissions1Excluded1
Food waste to landfill3Included, only applicable to Scenario 1
Food waste to compost3Included, only applicable to Scenario 2
Wastewater treatment3Included3
Road freight3Included

1Direct emissions from the café would not change after an implementation of a Green Machine and composting, and therefore not included in this case study.

2The GHG emissions associated with additional power requirements of running the Green Machine were assumed negligible at the small scale considered in this example, since the machine runs on less than NZ $2.00 per day (The Green Machine, no date). 

3Only GHG emissions associated with the 80 % by volume grey water product stream from the Green Machine were included. Emissions associated with wastewater from other operations within the café were considered negligible relative to the other major sources in this case study.

Compost can act as a carbon sink when applied to the soil, as the organic matter contained in the compost can transfer from liable fractions to more recalcitrant fractions and increase soil organic carbon over time. Such increases in soil organic carbon can take many years and is challenging to measure. This was conservatively assumed negligible and therefore not accounted for in this calculation.

2.1   Scenario Baseline

A café in Wanaka producing an average of 17.85 tonnes of food waste per year was considered. It was assumed that all of this waste is sent to the Victoria Flat landfill, 80 km outside of Wanaka. This landfill has methane gas recovery (Victoria Flats Landfill upgrade complete, 2021), meaning the GHG emissions from its disposal would total 5482 kg of carbon dioxide equivalents (kgCO2e).

Emission factors from Measuring Emissions: A Guide for Organisations provided by the New Zealand Ministry for the Environment (Ministry for the Environment, 2020) were used in the calculations. (

2.2   Technology

The Green Machine together with a Bokashi composting system can reduce GHG emissions through composting in accordance with the Clean Development Mechanism (CDM) outlined in the CDM project methodology AMS-III.F.

If a Green Machine is implemented, 80% of the waste by volume is sent to a wastewater treatment facility and the remaining 20% solid waste is processed in a Bokashi composting system. This reduces the GHG emissions to 12 kilograms of carbon dioxide equivalents (kgCO2e).

The freight transportation distance is estimated to be reduced to 10km, assuming that the food pulp from the Green Machine at the restaurant is transported to a local Bokashi composting site, such as an individual’s home or a local community garden.

Table 2 summarises the GHG emissions by activity for the two scenarios considered. The emissions of methane (CH4) and nitrous oxide (N2O) are reported in kgCO2e by scaling to their relative global warming potentials.

Table 3 summarises the reductions in GHG emissions achieved by implementing a Green Machine paired with Bokashi composting.

Table 2: Comparison of GHG emissions by scenario

ActivityQuantityUnitsEmissions% of Total
kgCO2kgCH4 (kgCO2e)kgN2O(kgCO2e)Total(kgCO2e)
Scenario 1
Waste Processing (Landfill)17,850kg5,337005,33797.3
Wastewater treatment0m300000.0
Scenario 2
Waste Processing (Bokashi)5,846kg00000.1
Wastewater treatment12.04m30.931.852.715.5047.3
Total 12

Table 3: Summary of GHG emission reductions with Green Machine and Bokashi composting

ScenarioTotal emissions (kgCO2e)Emissions reductions (kgCO2e)Emissions reductions (%)Potential reduction(tCO2e)
Scenario 15,487000
Scenario 2125,47599.85

3    Discussion

This case study found that GHG emissions could be reduced by over 99% by introducing a Green Machine and Bokashi composting system for food waste produced by a café in Wanaka, ultimately producing 5 tonnes of reductions per year. As indicated in Table 2, the methane emissions associated with decomposing food waste at the landfill site make up a significant portion of the total emissions. Therefore, the adoption of food composting is a key step to mitigate emissions. It is also important to note the absolute reduction in transportation-related emissions from shifting from a distanced landfill site to local composting facilities, with total emissions dropping from 150 to 6.1 kgCO2e.

Adopting a Green Machine in combination with a composting system has the potential to generate carbon credits since its implementation mitigates business as usual GHG emissions that would result from sending food waste directly to landfill. While the framework for a voluntary carbon market in New Zealand is yet to be established, such programs operate internationally.

In order for this project to qualify for originating credits, it would have to demonstrate adherence to the six Principles for Voluntary Climate Change Mitigation Claims published by the New Zealand Ministry for the Environment ( (Ministry for the Environment, 2022). Table 4 suggests the disclosures that should be made for a company, such as a restaurant, planning to implement a Green Machine and Bokashi composting system for a voluntary climate change mitigation claim.

Table 4: Disclosures for voluntary climate change mitigation claims

TransparentThe details of the activity should be publicly disclosed, including the boundaries of the activity and how it adheres to the remaining five principles of voluntary climate change mitigation.
Real, measurable and verifiedThe activity should be measured and verified by a third-party organisation that adheres to internationally recognised standards.
AdditionalThis activity goes beyond business-as-usual practices, which would otherwise send all waste to landfill, as there are no government obligations to defer waste from landfill nor are their largescale alternative food waste management options operating at a level that would be considered common practice.
Not double usedThe food waste can only be sent to compost once. A voluntary project may be required to only sell domestically to avoid a corresponding adjustment.
Address leakageThis project may incentivize a business not to address the fundamental problem of food waste, as the Green Machine and Bokashi composting system provides them with an ‘eco-friendly’ solution as well as potential profits through a carbon-crediting scheme. As part of this project, the company should outline strategies to reduce the amount of food waste they produce and also track this.
PermanentAn avoidance of emissions is permanent in nature.

4    Conclusion

In New Zealand hundreds of thousands of tonnes of food waste are being sent to landfill annually, producing methane as it decomposes anaerobically and as a result emitting a significant amount of greenhouse gases. By diverting waste from landfill with the implementation of a Green Machine paired with a Bokashi composting system, GHG emissions could be reduced by over 99%. Under a voluntary carbon market, should it ever exist in New Zealand, this project could generate carbon credits as long as it can prove that it follows the six Principles for Voluntary Climate Change Mitigation:

  1. Transparent
  2. Real, measurable and verified
  3. Additional
  4. Not double used
  5. Address leakage
  6. Permanent

The Green Machine with Bokashi composting is a small-scale methodology to avoid GHG emissions. It has the potential to be implemented at a local scale, for example individual cafés, restaurants and supermarkets. If these businesses cannot use the final Bokashi compost themselves, this end product can be offered back to the local community via a free collection service or donated to community gardens as a nutrient-rich soil conditioner.

One major limitation of this project’s success is the lack of national composting facilities. While some local councils provide subsidised Bokashi bins for private purchase, there are few larger scale composting collection and facilities available. In fact, the Christchurch City Council is currently the only council in the South Island that provides kerbside green wheelie bin collection at all.

By scaling the findings from this case study to a national average of 24,372 tonnes of food waste from all cafés and restaurants annually (Vacpack tackles food waste issue, 2021), we find that the implementation of this technology represents an opportunity to eliminate approximately 7,476 tCO2e of emissions. .


Ministry for the Environment. 2020. Measuring Emissions: A Guide for Organisations: 2020 Detailed Guide. Wellington: Ministry for the Environment.

Ministry for the Environment. 2022. Interim guidance for voluntary climate change mitigation. Wellington: Ministry for the Environment.

The Green Machine (no date) The Green Machine. Available at: (Accessed: 1 September 2022).

Vacpack tackles food waste issue (2021) Restaurant & Café. Available at: (Accessed: 1 September 2022).

Victoria Flats Landfill upgrade complete (2021) QLDC. Available at: (Accessed: 1 September 2022).

What is the total amount of food wasted in NZ? (2020) Love Food Hate Waste. Available at: (Accessed: 1 September 2022).

Merfield, C.M., 2012. Treating food preparation ‘waste’ by Bokashi fermentation vs. composting for crop land application: A feasibility and scoping review. The BHU Future Farming Centre. February 2012. Available at:

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