Enhancing a circular economy through the use of biochar and organic waste as an agro-ecological improver

We propose to conduct field soil experiments in the Rethymno municipality, Western Crete, Greece. These experiments will incorporate biochar into the soils, as it is well known that biochar can improve water and nutrient retention. Small scale field trials will use different quantities of biochar per square meter in combination with organic waste from the region. The field experiments will be monitored throughout the growing period to investigate water holding capacity, nutrient storage, carbon sequestration and nutrient/micro-nutrient uptake and soil health through microbiology. Organic food waste will be naturally dried and pulverised to enable easy breakdown in the soil. The experiments can be applied to a variety of agricultural crops in the region. Stable isotopes ratios of carbon, nitrogen and sulfur will be used to trace nutrient pathways from the organic waste through the soil and transfer into the plants. Many experimental trials will be undertaken to determine the ‘correct’ organic waste for each of the crops investigated. This will enable the Rethymno municipality, in partnership with the local agricultural community, to enhance and profit from using a circular economy in its society.

Previous experimental research undertaken by SIBL, Durham University has shown that biochar can improve the growth of agricultural crops, by increasing water holding capacity in the soil, taking up and storing more nutrients and micronutrients in the soil, and enhancing carbon capture. Climate change predictions estimate less rainfall in the Mediterranean and thus water scarcity will become a real issue – enabling water retention in the soil through biochar is one natural solution that can be used. These experiments will help the economy in the Rethymno Municipality become more self-sufficient, and sustainable by using its own organic waste to improve food security.

Prof Darren Gröcke is the Director of the Stable Isotope Biogeochemistry Laboratory (SIBL) at Durham University, UK. Over the past decade Darren and his group have worked on many aspects of agriculture. This has also included the use of biochar (in collaboration with Prof Mike Church – environmental archaeologist specialising in charcoal) as a method of carbon capture, improving soil health and plant growth. Currently, SIBL is working with a group of 50 farmers in Cumbria, England, researching sustainable and environmental methods in arable crops to improve soil health and food security in the region. Since much of this experimental research takes multiple years to perform, publications are in progress, but here are a few related to investigating modern and past agricultural amendment strategies:

Blanz, M., Gröcke, D.R., Martin, P., Church, M.J. (2024). The effect of seaweed fertilisation on sulfur isotope ratios (δ³⁴S) and grain size in barley: Implications for agronomy and archaeological research. Frontiers in Environmental Archaeology 3:1465082. https://doi.org/10.3389/fearc.2024.1465082

Styring, A.K., Vaiglova, P., Bogaard, A., Church, M.J., Gröcke, D.R., Larsson, M., Liu, X., Stroud, E., Szpak, P., Wallace, M.P. (2024). Recommendations for stable isotope analysis of charred archaeological crop remains. Frontiers in Environmental Archaeology 3:1470375. https://doi.org/10.3389/fearc.2024.1470375

Treasure, E.R., Gröcke, D.R., Lester, J.J., Bishop, R.R., Church, M.J. (2024). Further investigation into the impact of manuring on stable carbon (δ13C) and nitrogen isotope (δ15N) values in pulses: a four-year experiment examining Celtic bean (Vicia faba). Archaeological and Anthropological Sciences 16:130. https://doi.org/10.1007/s12520-024-02045-x

Gröcke, D.R., Treasure, E.R., Lester, J.J., Gron, K.J., & Church, M.J. (2021). Effects of marine biofertilisation on Celtic bean carbon, nitrogen and sulphur isotopes: implications for reconstructing past diet and farming practices. Rapid Communications in Mass Spectrometry 35:e8985. https://doi.org/10.1002/rcm.8985

Treasure, E.R., Gröcke, D.R., Caseldine, A.S. & Church, M.J. (2019). Neolithic farming and wild plant exploitation in western Britain: archaeobotanical and crop stable isotope evidence from Wales (c. 4000–2200 cal BC). Proceedings of the Prehistoric Society 85:193–222. https://doi.org/10.1017/ppr.2019.12

This proposal can be subdivided into three main budget streams:

(1) Experimental: this would involve the purchase and installation of environmental monitoring equipment, delivery and introduction of biochar into the soils. This would involve fieldtrips by the group to install the instruments and amend the soils for the experiments. This will also involve inspecting and working with organic waste suppliers to determine the best methods for processing the material as a soil bio-fertiliser. During this phase we will incorporate a citizen science aspect to the project where we will train local volunteers and/or employees of the Rethymno Municipality to regularly monitor the experiments and use some instruments that are manually used (e.g., carbon dioxide gas monitoring). Indicative costs for this aspect of the project are €105,000 which includes all costs related to fieldwork such as air-travel, accommodation and subsidence.

(2) Analytical: during the experimental period, many samples will be collected for elemental and isotopic analysis (e.g., soil, water, plants) and microbiology. This will be regularly done during the growing season and once again, in order to reduce travel costs and limit our own carbon budget, we would train local volunteers and/or employees of the Rethymno Municipality to collect these samples and post them to SIBL. Indicative costs for this aspect of the project are €55,000, including research assistant time to prepare all the samples in SIBL.

(3) Reporting: this study will benefit at least two undergraduate students in SIBL who will undertake dissertations on this project. Each will produce a report at the end of growing season 1 and 2, that will culminate into a single report that will be generated by Prof Darren Gröcke. The outcome of this study will also be presented to the Rethymno Municipality and local stakeholders in Western Crete to develop an island-wide model for environmental sustainability, a circular economy and food security for the island. Indicative costs for this aspect of the project are €20,000.

A total indicative budget of €180,000 will enable this 2+-year experimental project on using organic waste as a bio-fertiliser in agriculture. Biochar is included to enhance water and nutrient retention in the soil. The results of this study will enable the of the Rethymno Municipality to explore and use a circular economy model to enhance sustainability and food security on the island of Crete. SIBL looks forward to working with the Rethymno Municipality on this exciting, sustainable and innovative project.