Carbon footprint of coffee

What a carbon footprint measures#

A carbon footprint adds up the greenhouse gases released over the life of a product. ISO 14067 sets out how to quantify and report it, consistently with the life-cycle assessment standards ISO 14040 and ISO 14044.¹ It covers one impact category only: climate change.¹ Water, biodiversity, and social or economic effects are outside its scope.¹

Results are given in kilograms of carbon dioxide equivalent (kg CO₂e). This unit expresses any greenhouse gas as the amount of carbon dioxide with the same effect on climate over a set time.⁴ In coffee studies, global warming potential (GWP) is the impact category most often reported.⁷

A footprint is always a footprint of something. It can be a hectare, 1 kg of green or ground coffee, or a volume of drink.⁷ It also depends on where the study starts and stops. The same coffee can therefore appear with very different published numbers.⁷

How a life-cycle assessment is built#

A life-cycle assessment (LCA) follows the steps that ISO 14040 and ISO 14044 describe. These are goal and scope, inventory analysis, impact assessment, and interpretation.^2,3 Three choices in the first step matter most when coffee studies are compared.⁷

• Functional unit. It is the “quantified performance of a product system for use as a reference unit”, in the European Commission’s glossary based on ISO 14040.⁵ Coffee studies have used hectares, kilograms of cherry, parchment, green or ground coffee, and volumes of drink.⁷
• System boundary. This sets which stages are counted. Some coffee studies stop at the farm gate; others run from cradle to grave, that is, to the cup and the waste.⁷ The farm stage was not always fully included; in one study, energy accounting started with cherry processing.⁷
• Allocation. A process that yields more than one product shares its emissions between them; this sharing is called allocation.⁶ In a 2024 review of coffee LCAs, most studies did not consider or mention any co-product allocation.⁷

ISO 14040 describes the framework; it does not prescribe the methods for each phase.² Two studies that both follow it can therefore still differ.^2,7

Where the emissions arise#

A 2024 systematic review gathered 34 coffee LCAs covering 234 coffee systems.⁷ It describes where, along the chain, the emissions arise.⁷

• On the farm. Land-use change, fertilisers and washed processing (“wet processing” in the review) were the main contributors to the footprint of green coffee.⁷ Land-use change here means clearing land to establish the plantations.⁷ Leaving it aside, synthetic fertilisers contributed a median 66%, counting both their manufacture and their emissions in the field.⁷ Field trials and farm surveys point the same way (see Deep dive).^12,13
• At the mill. The review names washed processing (“wet processing” in its words) among the main contributors.⁷ It found it modelled inconsistently across studies.⁷
• In transport. Where coffee was shipped by sea, transport added a few percent (median ≈3%, up to 12%).⁷ Where air freight was assumed, transport could make up more than 73% of the footprint.⁷
• At the roastery. Roasting and grinding together contributed a median 8% in cradle-to-grave studies.⁷
• Packaging. Packaging contributed a median 9–18%; the higher figure applied to single-serve pods and capsules.⁷
• In the cup. Brewing, cup washing and waste management each contributed about 18% (median).⁷ Heating water was the first or second contributor to energy use, depending on the drink and on whether a machine or a kettle was used.⁷

Taken over the whole chain, green coffee production was the largest contributor, with a median share of 63%.⁷ Drinks with milk were outside that review. Two studies that included milk found that it raised the footprint of a drink well above that of an espresso.^8,11

The figure shows one study’s result stage by stage. In that study, flying the coffee to the UK made up most of the conventional footprint.⁸ The authors chose air freight because, in their words, “retailers are increasingly transporting coffee beans via freight flight to get fresher coffee”.⁸ The review cited above excluded this study from its averages (see Contested).⁷

Why studies disagree#

The review found that GWP “varied greatly at both the farm and drink levels”.⁷ For green coffee it ranged from 0.15 to 14.5 kg CO₂e per kg (median 3.6).⁷ For drinks, it ranged from 2 to 23 kg CO₂e per kg of coffee consumed (median 8.8).⁷ It names several reasons.

• Land-use change. Counting it raised results up to four-fold; it made up 1–75% of the footprint of green coffee.⁷
• Field emissions. Most studies did not say whether indirect nitrous oxide, or carbon dioxide from urea and liming, was counted.⁷
• Washed processing. Fermentation and wastewater emissions were not modelled consistently, and some studies left them out.⁷
• Functional unit and dose. No study defined its functional unit by moisture or by sensory quality.⁷ How much coffee goes into a cup, and how much it is diluted, changed results but was mostly not built into the functional unit.⁷
• Transport mode. Ship transport was negligible to a few percent; air freight could exceed 73%.⁷ One study assumed that freight flights emit about 100 times more CO₂e per km than cargo ships.⁸
• Background assumptions. Energy results depended on the electricity mix assumed.⁷

Stages a roaster or café controls#

The studies attribute shares of the footprint to stages; they do not rank businesses. Read that way, the stages a roastery or café runs itself carried smaller shares than the farm.⁷ Roasting and grinding contributed a median 8%, against 63% for green coffee production.⁷

• Which coffee, from where. Green coffee production carried the largest share.⁷ According to the research programme behind a 2014 farm study, commercial polycultures are among the most promising ways to grow coffee with a low footprint.¹⁴
• How it travels. Shipping by sea added a few percent; air freight could dominate.^7,8
• Packaging. Single-serve pods and capsules carried the largest packaging share.^7,10
• How it is brewed. Heating water and machine energy were a major part of the use phase.^7,8 One 2009 study named the amount of extra water boiled as a key parameter.⁹
• Milk. In two studies, drinks with milk had a clearly higher footprint than espresso.^8,11 One named cow’s milk among the raw materials with the highest emissions.¹¹

The authors of the 2020 study list ways to lower its footprint: optimal use of agrochemicals, less packaging, more efficient water heating, renewable energy, roasting before export and carbon offsetting.⁸ These are the authors’ suggestions from one modelled supply chain. Claims about offsetting are covered in the planned entry on sustainability claims.