From by-product to bedrock - can reusing sugar waste recreate chalk grassland?

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Grassland

Arena case study

Could a by-product from sugar manufacturing processes be used to create chalk grassland, a richly diverse habitat disappearing from our landscape?

Background

Over the past century, 97 per cent of wildflower meadows  in the UK have been lost, including substantial declines in lowland chalk grasslands which host a rich diversity of species of great biodiversity value. Projects seeking to address the decline of chalk grassland have used a variety of techniques, including importing chalk for habitat creation, but chalk extraction comes with significant economic and environmental costs. There is increasing evidence that aggregates made from recycled waste products can be used for green infrastructure (e.g. green roofs, Sustainable Drainage Systems (SuDS) etc) and habitat creation projects, offering a sustainable alternative to mining new materials.

Grassland

The Sustainability Research Institute (SRI) worked with Tate & Lyle to evaluate the performance of a calcium carbonate (chalk) by-product from their manufacturing process as a potential substrate material for creating chalk grassland habitat.

This would offer the company opportunities to:

  • develop a circular economy model that transforms a company waste material into a new company product
  • generate an initial evidence base of proof of concept
  • understand the benefits of a product that can support conservation of important biodiversity.
Tate and Lyle logo and some soil

How ARENA was able to help

The SRI has a strong team of professional ecologists with a track record of working on innovative green infrastructure interventions in urban and rural environments and in partnership with commercial enterprises. Working with Tate & Lyle, and in collaboration with the Grass Roof Company (another business receiving support through the ARENA project), we established a growth trial field experiment, to assess the performance of their calcium carbonate by-product as a substrate for chalk grassland creation.

SRI ecologists:

  • developed the experimental design, using a series of replicated mounds sown with a chalk grassland seed mix
  • carried out vegetation surveys during summer of 2021 to monitor habitat development and evaluate its suitability as chalk grassland growing medium
  • provided guidance on next steps to get the product to market..

A field experiment was created to assess the performance of Tate & Lyle’s by-product as a growing medium for chalk grassland habitat creation.

Image of Tate & Lyle field experiment

The results

The results from the field trial confirmed three key findings for the Tate & Lyle chalk by-product:

  • it performed as an effective basic growing medium under the experimental conditions
  • the vegetation composition was significantly different to the topsoil ‘comparison’ mounds
  • a greater number of the target chalk grassland species were recorded on Tate & Lyle’s product.

The growth trial confirmed Tate & Lyle’s by-product as a viable growing medium for chalk grassland species, and identified next steps to explore ways to improve its performance for creating a proxy chalk grassland habitat.

Three sets of grass growing

Overall, the growth trial results were encouraging and indicated that Tate & Lyle’s product has potential as a growing medium for creating a proxy chalk grassland habitat. Nonetheless, the pilot study also identified unexpectedly vigorous vegetation growth on the Tate & Lyle by-product, with a predominance of grasses reducing wildflower development within the sward. A key factor determining the species richness of chalk grassland is low soil fertility that suppresses grasses from dominating, allowing a diverse range of herbs and other plants to flourish.

Next steps

In light of these findings, the following areas were recommended for further research: 

  • Isolate the material from underlying substrate: to explore the extent of the effect that the underlying substrate may have on vegetation development (e.g. use impermeable membranes, or trial the material as a component of green roofs).
  • Reduce/remove grasses from seed mix: to investigate if this enables a greater range and abundance of wildflower species to establish and produces a habitat more akin to a herb-rich chalk grassland.
  • Scale up the study: create larger, replicated experimental plots and extend the duration of the study for more than a single growing season to build on the promising evidence from this pilot study.

This ARENA business support has already provided a springboard for further field trials of the product, including a green roof research project on the roof of Tate & Lyle’s factory in Docklands, in collaboration with UEL’s Landscape Architecture students and researchers.

References

  • Connop, S. and Nash, C. (2018) Blandscaping that Erases Local Ecological Diversity. The Nature of Cities essay. Available from: https://www.thenatureofcities.com/2018/01/09/blandscaping-erases-local-ecological-diversity/
  • Haiyan Li, Yihui Zhang, Liyuan Wu, Yi Jin, Yongwei Gong, Angzhen Li, Jinxi Li, Fei Li, (2021) Recycled aggregates from construction and demolition waste as wetland substrates for pollutant removal. Journal of Cleaner Production 311, 127766
  • Molineux, CJ, Gange, AC, Connop, SP and Newport, Dj (2015) Using recycled aggregates in green roof substrates for plant diversity. Ecological Engineering 82, 596-604.
  • Molineux, CJ, Fentiman, CH, Gange, AC (2009) Characterising alternative recycled waste materials for use as green roof growing media in the U.K. Ecological Engineering 35 (10), 1507- 1513.
  • SoN (2019) State of Nature – UK Report. Available from: https://nbn.org.uk/wp-content/uploads/2019/09/State-of-Nature-2019-UK-full-report.pdf