The carbon footprint of organic vegetables needs to be improved

The demand for organic fruit and vegetables is growing significantly, but updated knowledge is needed about the climate impact of production of organic vegetables. For organic vegetables grown and harvested in greenhouses, there is another challenge. New EU regulation means that in the future, production must take place in open systems, i.e. with direct access to soil. The question is how this will influence the carbon footprint - and the leaching of nutrients to the environment? Researchers from AU, in collaboration with the industry, are looking into these questions within the framework of the ClimateVeg project.

20 November 2020 by Camilla Mathiesen

Associate Professor and Science Team Leader Hanne Lakkenborg Kristensen from the Department of Food Science at Aarhus University leads the ClimateVeg project. She explains:

- There is only few so-called life cycle assessments (LCA) on Danish produced vegetables. So far, focus has primarily been on milk and meat production. When we are moving towards a much more plant-based diet, we also need to pay attention to the vegetables, and here we are missing updated figures.

Some of the biggest challenges for the climate profile of organic vegetables are the high risk of nitrogen leaching when it comes to open-field vegetables - while a high level of energy consumption is the main problem when it comes to vegetables grown in greenhouses.

Several major organic vegetable producers and distributors are involved in the project, Månssons by RootConsult, and Aarstiderne as representatives for the open-field producers and Økogården (Alfred Pedersen & Søn) and Lykkesholm for the greenhouse producers.

Consultant Dorrit Andersen from RootConsult, in the project representing Månssons, one of Denmark’s largest vegetable producers, says:

- At Månsson, we work dedicated with organic and sustainable vegetable production. The focus is constantly on developing the production systems and on new products. By participating in the ClimateVeg project, we expect the project to contribute to this development, where we hope to develop some tools and to gain insight into assessments that will make it possible to increase the favorable climate perspective for the company and the surrounding community.

In ClimateVeg, the researchers, Marie Trydeman Knudsen and Lisbeth Mogensen from the Department of Agroecology, Aarhus University will be responsible for the life cycle assessments. They will look at key figures for resource use and yields from the various productions, and the climate and environmental impact will then be calculated on this basis. There is a special focus on the nitrogen accounts, and leached nitrogen, as well as on energy consumption and vegetable yields.

In collaboration with two related projects, SUREVEG and GREENRESILIENT, both of which are part of the European ecological research program CORE Organic COFUND, the researchers will carry out additional experiments outdoors and in greenhouses, as part of the ClimateVeg project.

The crop rotation into the greenhouse

In GREENRESILIENT , researchers work on using agroecological principles in the greenhouse, including crop rotation and flower stripes. These are new practices attempting to adapt the organic greenhouse production to the new EU regulation from 2021 (productions started after 28 June 2017) or 2030 (productions started before 28 June 2017). The researchers are also trying to find crops that can be grown in the greenhouses - without heating in the off-season - something that can make a major difference for the growers in satisfying the Danish market.

In SUREVEG (indsæt link), they work with crop combination of e.g. beetroot and white cabbage with a focus on new fertilizer strategies that are organic and plant-based while stimulating the soil's fertility and carbon sequestration in the longer term.

The ClimateVeg project provides an opportunity to expand the large field and greenhouse trials already established in GREENRESILIENT and SUREVEG, thereby investigating effects that require several years of cultivation to make an impact. These include soil quality parameters and effects of fertilizer strategies and crop rotation.

-We will also supplement with pot experiments and investigate the interaction between different field soils and organic fertilizers' turnover. The mineralization of nutrients and microbial activity will be in focus, says Hanne Lakkenborg Kristensen. Here, different types of plant-based fertilizers will be tested, as the goal is to break free from the current use of conventional livestock manure.

Smarter fertilizer

In ClimateVeg, the researchers will make new life cycle assessments (LCA) and suggestions how to reduce the climate impact. In particular, there is room for improvement when it comes to nitrogen loss. Here, the type of fertilizer, and when it is applied, is central.

-The problem is to fertilize precisely, Hanne Lakkenborg Kristensen explains and continues:

-It is difficult to predict how much "power" is in the soil in advance. It is easy to see when the plants lack fertilizer, but you do not see when the plants have received too much, because the leaching is not directly visible. That is why we in ClimateVeg are trying to differentiate the fertilizer so that fast-releasing fertilizer is given by precision in the spring. Here different types of fertilizers must be tested. And in the autumn, slow-releasing fertilizer is given in the form of compost, which has a soil-improving effect.

It is important to include the pot experiments, as they allow us to examine the reaction of different soil types in relation to when the nitrogen is released from fertilizers and how quantity, quality and other factors come into play.

-A good fast-releasing, plant-based fertilizer type is red clover when it is harvested while the nitrogen content is high relative to the carbon in the plant material. The problem is that there is no clover in early spring. Alternatively, you can silage the clover so that it is stable and ready when the plants need it. And then it must be combined with a winter cover crop to retain the nitrogen in the soil. There must always be a balance between carbon footprint, economy and what the farmer can handle in practice, Hanne Lakkenborg Kristensen explains.

The goal of ClimateVeg is to document the climate and environmental profile of Danish organic vegetables, but also to identify where it pays to invest in improvements.

For further information:
Hanne Lakkenborg Kristensen
Aarhus University
Department of Food Science
Hanne.Kristensen@food.au.dk

About the three projects:

ClimateVeg:
Project manager:
Hanne Lakkenborg Kristensen, Department of Food Science, Aarhus University

The project is part of the Organic RDD 4 program, which is coordinated by ICROFS (International Centre for Research in Organic Agriculture and Food Systems). The project has received grants from the Green Development and Demonstration Program (GUDP).

Project period: 2019-2022

The carbon footprint of organic vegetables needs to be improved

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