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Is grass the new gold?

Green fields of grass instead of golden cornfields can help reduce Denmark’s emission of climate gasses by as much as 20 percent but will require further development of current technologies and changes in agricultural practices.

[Translate to English:] Danmark kan fastholde sin fødevareproduktion, selvom der dyrkes græs i stedet for korn. Foto: Jesper Rais

Agriculture can help reduce Denmark’s emission of climate gasses by as much as 20 percent without affecting food production. This reduction roughly equals the total greenhouse gas emissions from the entire agricultural sector. The solution is an increased biomass production combined with biomass refining which makes the biomass suitable for food, feed, fuels and bio-based materials. 

Much of the solution is – literally – green. It comes in the form of grass. Permanent grasslands can be worth their weight in gold in relation to climate, environment and food production. In order to achieve this, further development of existing technologies is required as well as adjustment of agricultural cultivation systems and increased development within the bio-refinery sector.

 Improved utilization of resources

It has already been said that increased biomass production is the way to go. In October 2016 scientists from Aarhus University and the University of Copenhagen published a revised version of the “+10 million tonnes study”. 

One of scientists behind the report, Senior Researcher Uffe Jørgensen from the Department of Agroecology at Aarhus University, explains: 

- It is important to utilize our limited resources in the best possible way to produce feed, food, energy and other materials. . In Denmark we can produce 8-10 million tonnes of biomass for bio-refining without reducing our food production and without using more land. Grass is an important part of this solution, Uffe Jørgensen says. 

It is difficult to increase biomass production significantly within the current agricultural framework because it is not possible to intensify the present production sufficiently e.g. by using more pesticides and fertilizers. However, increased biomass production can be achieved by changing production systems, developing and applying suitable crops and altering land use.   

Grass benefits the climate

In order to reach this goal it is important to increase grass acreage. Grass should replace crops such as grains, rapeseed and corn. Growing grass can increase the productivity in the field with optimized choice of cultivars and management. As this allows for an increased harvest of dry matter per ha, the increased growth can be used for new products. This means that Denmark can maintain its food production even though grass is grown instead of cereals.  

Permanent grasslands are better than annual crops at retaining carbon in the soil. This is beneficial to soil quality and fertility. In addition, carbon retained in the soil is not converted to the climate gas CO2

By means of biorefinery it is possible to extract protein from grass and thus produce Danish protein for livestock feed and protein products for food production. This can reduce the Danish import of soybeans, which currently takes up areas in primarily South America corresponding to the size of Zealand.

An increased Danish biomass production will benefit more than the climate. Focusing on biomass will help reduce nitrate leaching to the aquatic environment as grass is able to replace grains in the most vulnerable areas. This will halve nitrate leaching compared to the traditional cultivation of grains and rapeseed. Compared to maize the reduction of nitrate leaching will be even more significant. Reduced nitrate leaching will also reduce the risk of generating the potent climate gas nitrous oxide. 

New thinking, new knowledge and new methods required

How can the agricultural sector start converting from grain to grass? 

- First and foremost, the methods used to produce high-value products from grass – primarily protein – should be further developed, allowing us to establish an industry to use the grass produced, Uffe Jørgensen explains. 

- At the same time, a range of plant production technologies and systems need to be developed before we can realize and implement all the new product chains. For instance, we need systems to handle grass in long-term rotation. We often experience that permanent grassland yields decrease. We do not exactly know the reason for this or how to prevent the problem, but we are currently looking into it, he explains. 

One of the possibilities that the scientists want to examine is rotation of permanent grasslands every five to eight years followed by the sowing of new grass in combination with cereals sown in the spring. In the first year, the grains would be harvested in the autumn and the grass harvested in subsequent years. The scientists will examine the impact of this system on e.g. organic matter in the soil and on the emission of the greenhouse gas nitrous oxide. 

Other research projects at Aarhus University aim to develop high-yielding grasses with a high content of extractable protein (”Super grass to increase cow milk production and reduce methane emissions”), examine the optimum ratio between clover and grass in order to minimize nitrogen fertilization (“Nitrogen, clover, camera and image analysis all come together”), optimize the content of extractable protein, and identify the optimum harvest time in order to achieve as much extractable protein as possible. 

Other projects support the development of new soil improvement products and methods to maintain organic material (C) in the soil.

Significant need for research and development

More research and development is needed within the agricultural sector in order to realize the full technological and environmental potential of an increased biomass production. 

The wish list is exhaustive. It includes e.g. developing grain crops with a higher straw yield, developing grasses that are robust towards too little and too much water and heat, developing new cultivation systems that can handle increased straw yields without reducing grain yields, developing new harvest and storage technologies, studies of whether it is the grass or the soil that grows “tired” after some years, life cycle assessments in relation to the various systems and their environmental impact, and assessments of the systems’ impacts on society. 

- Even though grass systems convert nitrogen fertilizer to protein very efficiently and ensure a very low level of nitrate leaching (on the same level as nature areas and forests), one of the challenges in relation to these systems is that there is a risk of high nitrous oxide emissions. So far, we have simply used standard factors when calculating nitrous oxide emissions from cut grass systems, but we have recently initiated a PhD project that will examine more precisely the actual amount of nitrous oxide emissions. We will also test whether the issue can be addressed by adding nitrification inhibitors to the fertilizer, or by using legume plants to provide nitrogen to the systems, says Uffe Jørgensen and continues: 

- We need more knowledge in certain areas, but grass is still a well-known crop that farmers are familiar with managing. The problem is that currently there is no market for grass. Furthermore, research in the extraction of protein from grass has only been going on for 2-3 years in Denmark, so we still need more experience in this area. There is a significant need for research and development in relation to technology and infrastructure for biological and chemical conversion of biomass. 

Another challenge is motivating farmers. 

- Ten million tons of biomass can supply about 20 percent of our present natural gas consumption and 30-50 percent of our consumption of petrol and diesel. The agricultural sector supplies the biomass but the reduction of climate gas emissions is mainly credited to the energy sector. The energy sector gets the quotas and the farmers nothing. We need to establish an incentive in order to get the agricultural sector on board, says Uffe Jørgensen.

For further information:

Read more about climate change and agriculture in DCA's theme.

Read the scientific article Perennial Grasses for Sustainable European Protein Production


Senior Researcher Uffe Jørgensen, Department of Agroecology, e-mail: uffe.jorgensen@agro.au.dk, telephone: +45 8715 7729, mobile: +45 2133 7831