Research & reports

Bart Neuts, Steven Valcke, Clio Lambrechts, Vincent R. Nijs, Jan Van Praet · · Europe

This study describes a participatory inquiry conducted in the summer of 2021 at St Godelina’s Abbey in Bruges, Belgium, where visitors co-created 4,784 scenarios for the heritage site's future development. A panel of 40 experts further explored these scenarios, leading to an architectural design that integrates a community garden, orchard, and other elements. The process is presented as a best practice for citizen participation in redeveloping cultural sites, though limitations include significant data collection and analysis efforts, making it impractical for smaller initiatives.

Ayşe Kaplan Sarısaltık, Ufuk Sarısaltık · Cleaner and Responsible Consumption · Turkey

This qualitative study explored the role of ODTÜ Bostan, a community garden at the Middle East Technical University in Turkey, in promoting sustainability education, ecology, and food consumption practices. Operating for ten years, the garden not only enhances participants' sustainability competencies but also serves as an educational laboratory, demonstrating the potential of community gardens to address global challenges like climate change and biodiversity loss. The research employed autoethnography, thematic analysis of eight semi-structured interviews, and content analysis of archival data.

Diana Krabbendam, Emiel Wolf, Bernie Deekens, Rosalie Bak, Hans Krikke · SpringerBriefs in applied sciences and technology · Netherlands (Amsterdam)

This chapter outlined activities for citizen-led projects in the Wildeman neighborhood in Amsterdam. The main challenges identified were a lack of trust and community feeling among inhabitants, a lack of involvement and ownership in neighborhood developments, and fragmented existing community activities and services.

Géant Basimine Chuma, Jean M. Mondo, Adrien Byamungu Ndeko, Etienne M. Akuzibwe, Espoir Mukengere Bagula, Gustave Nachigera Mushagalusa · Discover Sustainability · Democratic Republic of Congo (Bukavu City)

This study investigated the quantity, composition, and disposal practices of domestic waste in Bukavu City, Eastern D.R. Congo. Findings revealed significant challenges in waste management infrastructure and practices, showing that approximately 5% of waste undergoes composting, while 10% is used as livestock feed, 66% incinerated, and 17% buried. Waste management is primarily handled by children (82%), with very limited involvement from non-governmental organizations.

Holger Braun, Dorothee Apfel, Benedikt Rilling, Carsten Herbes · Cleaner and Responsible Consumption · Germany

A study with 44 hobby gardeners in Germany found that substrates are not a major part of gardeners' social interactions, and price is the dominant purchase criterion for substrates, with sustainability not playing an important role. Although basic knowledge about peat is widespread, purchasing substrates is a utility-driven process with mostly passive information behavior.

Cosimo Dondini, Xavier Úbeda, Giacomo Certini, Marcos Francos · Journal of Soils and Sediments · Spain (Barcelona)

This study analyzed soils from ten urban gardens in Barcelona, Spain, with a special focus on possible contaminants. Irrigation water was also analyzed, and some of the waters contained a high concentration of salts and nitrites, which are listed as a pollutant. While three tests for heavy metals did not attest to significant pollution, other toxic elements not considered in this study could come from road transport gases or the port of Barcelona. Overall, the soil quality was concluded to be suitable for growing vegetables.

Simone Trimmel, Stefan Wagner, Laura Feiner, M. Feiner, Daniela Haluza, Rebecca Hood‐Nowotny, Ulrike Pitha, Thomas Prohaska, Markus Puschenreiter, Philipp Spörl, Andrea Watzinger, Elisabeth Ziss, Johanna Irrgeher · Environmental Science and Pollution Research · Europe

A study of urban gardens in Vienna, Austria, building on a previous study of eleven gardens in the city that found elevated lead (Pb) levels in some soil and plant samples. This work examined the elemental composition of soil and plants from two of the affected gardens one year after compost amendment. ICP-MS analysis of tomato fruit skin, pulp and seeds showed only minor variations in elemental composition unlikely to affect food safety, whereas radishes showed a tendency toward contaminant accumulation in root tips and leaves. Washing lettuce significantly reduced levels of potentially toxic elements including Be, Al, V, Ni, Ga and Tl, underscoring the importance of washing garden produce before consumption; compost amendment was associated with reduced Zn, Cd and Pb levels in radish bulbs. Lead isotope ratios in soil and spinach leaf samples from the earlier study, assessed by MC-ICP-MS, showed a direct linkage between the Pb isotopic signatures in soil and spinach leaves, supporting their use as tracers of Pb sources in the environment.

Remigio Paradelo, Cecilia Herbón, María Teresa Barral · Journal of Soils and Sediments · Spain

This study examined 64 urban soils in Santiago de Compostela, Spain, across different parent materials and land uses, assessing physical properties including bulk density, porosity, water holding capacity, aggregate stability, water-dispersible clay, permeability, and resistance to penetration in field and laboratory measurements, along with erosion risk estimated via the K factor of the RUSLE. Results show heterogeneous physical properties typical of urban soils; high organic matter and iron content were associated with low bulk density and high aggregate stability. Compaction issues were widespread but land-use dependent: soils under urban agriculture had higher permeability and lower compaction than urban grasslands and forests. High infiltration despite compaction was attributed to abundant coarse fragments and preferential flow paths. Overall erosion risk was found to be low based on K factor values, but the study concludes that sound management remains essential because relief, climate, and human behavior can increase erosion risk at specific points.

Anne-Kristin Løes, Sebastian Eiter, Tatiana Rittl · Environmental Sciences Europe · Europe

Using soil data from ten peri-urban case farms near Oslo and Bergen, Norway, this study estimated how quickly potentially toxic element (PTE) concentrations would rise in soil under intensive application of compost or digestate from food waste, composted garden waste, or horse and poultry manure applied annually to meet a theoretical carrot crop's nitrogen, phosphorus and potassium demand. Under this intensive fertilization scenario, Norwegian soil quality limits for PTEs would be reached within 20-85 years, faster in soils with more organic matter, with limits reached first for copper and zinc, both essential micronutrients. The urban waste-based fertilizers were also found to be poorly balanced in macronutrients, with rates covering potassium demand leading to high phosphorus and nitrogen surpluses. The study concludes Norway's PTE regulations are stricter than the EU's and do not support recycling organic matter and nutrients from urban waste.

David Berná Serna, Sara Sama Acedo, Patricia Homs Ramírez de la Piscina · Revista Española de Sociología · Spain

Against the backdrop of the current eco-social crisis, this article analyzes the "eco-transformative capacity" of collective initiatives in three Spanish case studies: neo-ruralization and natural wine production in the Sierra Oeste de Madrid and southern Sierra de Gredos, agroecological supply systems in Catalonia, and community urban gardens integrated into a municipal program in Madrid. The analysis focuses on the motivations, challenges, and limitations agents encounter while practicing sustainable ways of dwelling, producing, and consuming, and on their relationship to public institutional agendas on eco-social transition.

Victor Crespo de Oliveira, Leonardo França da Silva, Érika Manuela Gonçalves Lopes, Ana Carolina Chaves Dourado, Matheus Mendes Reis, Bruna Nogueira Rezende, Letícia Duron Cury, Cássio Furtado Lima, Fabiane de Fátima Maciel, Silvana Ferreira Bicalho, Ariadna Faria Vieira · · Europe

Noting that global population growth is raising concerns about the sustainability of cities and soils, climate change, and food access and security, and that many urban areas face challenges related to their food supply infrastructure, this paper positions urban agriculture as a potential contributor to food security and income generation for impoverished households, while noting that conventional agriculture contributes to soil erosion and soil/groundwater pollution, and that climate change disrupts animal life cycles and drives species extinction, reducing food availability for humans and other organisms. Within this framing, the paper presents aquaponics as a method integrating urban agriculture for plant cultivation with safe fish production, and reports a project to develop and install an optimized aquaponics system at the School of Engineering, Polytechnic of Porto (ISEP). The soil-less vertical garden was built using two tanks holding approximately 2,000 liters of water, spanning three floors with three planter boxes and more than 120 positions for growing vegetables. Pedagogical activities were also carried out, involving students from Bioresources, Chemical Engineering, Biomedical Engineering, Electrical and Computer Engineering, Mechanical Engineering and Informatics Engineering.

Gemma Nohales, Mike Stinavage · Zero Waste Europe · Europe

The EU mandated separate collection of bio-waste across all Member States from 31 December 2023, but a LIFE BIOBEST survey of 14 Member States found economic, legal/administrative, organisational and technical barriers present in 86-100% of sampled countries. Only 7 of 27 Member States fully met the 2020 recycling targets, and only 9 are on track for the 2025 targets.

Gabin Colombini, Fatima Senouci, Cornelia Rumpel, Sabine Houot, Philippe Biron, Axel Felbacq, Marie-France Dignac · Environmental Pollution · France

A 2024 analysis of archived soils from a long-term field experiment in France that received three urban composts — municipal solid waste compost, biowaste compost, and a sewage-sludge-plus-green-waste compost — over 21 years. Density fractionation followed by oxidation isolated 1,417 coarse microplastic (CMP) particles, identified by Py-GC/MS; different compost types produced different accumulation levels, and CMP content in soil rose over time. After 21 years the measured number of CMP particles matched estimates derived from compost inputs, but the measured mass did not for any of the three composts, which the authors attribute to biotic transport or to weathering and fragmentation making particles smaller. No difference in temporal pattern was found between films and fragments. The value of the study is long-term evidence that returning urban organic matter to soil also imports plastic; note that the site is farmland, not a city garden, so the figures cannot be transferred directly to citizen composting.

Daniel González, Raquel Barrena, Javier Moral-Vico, Ignacio Irigoyen, Antoni Sánchez · Waste Management · Spain

A 2024 study that measured methane and nitrous oxide (the main greenhouse gases), ammonia, volatile organic compounds (VOCs) and odour from several operating community composting sites in Spain treating kitchen waste, leftovers and household biowaste. Greenhouse-gas emission rates ranged from 5.3 to 815.2 mg CO₂eq per kg volatile solids per day and odour rates from 69.8 to 1,088.5 odour units on the same basis; both fell as temperature and biological activity declined with composting progress, and both were generally lower than rates reported for open-air full-scale composting plants. VOC families were most diverse in the early composting phases, while terpenes — limonene, α-pinene and β-pinene — were the most abundant throughout. The authors start from the observation that scientific data on gaseous emissions from community composting are scarce, which means that arguments about odour nuisance to neighbours have until now lacked measured reference values.

Alves, D., Villar, I., Mato, S. · Environmental Science and Pollution Research (Springer), 31(7):9873-9885 · Spain / Europe

A study comparing methodology, bulking agents, and compost quality across community composting centres (CCC) and community gardens used by local governments to treat biowaste. It shows how population density and the presence of green areas determine the siting of decentralized local composting infrastructure.

Kizza-Nkambwe S., Mpewo M., Kasima J. S., Mfuranzima K. · Sustainable Environment · Mukono, Uganda

Assesses compost quality from a waste composting facility in Mukono municipality, central Uganda, analysing physicochemical parameters and heavy metals and arsenic in mature compost.

Mustafa Ali, Lenny Koh, Adolf Acquaye, Jonathan R. Leake, Jacob Nickles, Toby P. Evans, Gareth Roberts, Douglas Kemp · The International Journal of Life Cycle Assessment · United Kingdom (Sheffield)

This study conducted an integrated environmental and economic assessment of organic peri-urban horticulture using primary data from a farm in Sheffield, UK. A hybrid life cycle assessment (LCA) found that the global warming potential (GWP) for case study tomatoes was 3.53 kg CO2-eq, which was 1.87 times higher than imported Spanish tomatoes. Economic analysis showed that the marginal increase in the prices of tomatoes and courgettes from the case study farm was 4.6 and 5.15 times less than the market prices, leading to the conclusion that the studied production system is economically and environmentally sustainable compared to the existing scenario.

Michele D’Ostuni, C. Stanghellini, A. Boedijn, Leonardo Zaffi, Giuseppina Pennisi, Francesco Orsini · Sustainable Cities and Society · Netherlands (Amsterdam)

The feasibility of using urine and greywater streams as nutrient solutions in a theoretical model of Building-Integrated Agriculture in Amsterdam was evaluated. Results showed it is feasible to use urine and greywater as nutrient solutions; however, treated urine had higher macronutrient concentrations than literature fertilizer recipes, requiring dilution with increasing amounts of greywater to match N or P concentrations. Consequently, P deficiencies in plants or excessive N concentration were found in the final wastewater-based nutrient solution.

Abigail Schoneboom, Daniel Mallo, Armelle Tardiveau · Journal of Classical Sociology · United Kingdom

This sensory ethnographic study, using pinhole photography, explored how time is experienced by unemployed volunteers at a community garden in the north-east of England. It found that the garden's ability to provide meaningful time is rooted in its food-growing and composting cycles, as well as enduring elements like mature trees and volunteer-made structures. The study argues that urban community gardens offer an "elongated present" that fulfills individuals and sustains community and nature.

Chloé Duffaut, Florence Brondeau, Julien Gasparini · Urban Agriculture & Regional Food Systems · France (Ivry-sur-Seine)

This study tested the effects of feral pigeon guano as a fertilizer on cherry tomato plants in an urban environment on a rooftop in Ivry-sur-Seine, France. In June 2017, 15g of guano was added to 15 cultivation bags, while 15 control bags received only water. After 15 days, guano-treated plants were taller and tended to have more flowers, and the total number and mass of harvested cherry tomatoes were one to two times higher than the control. However, the average mass per fruit was not affected by the treatment. The study concluded that pigeon guano is an efficient local fertilizer for cherry tomato plants in urban areas.

Lisa Mølgaard Hald, Luke John Schafer · Agrosystems Geosciences & Environment · United Kingdom (Dartington)

This study examined soil organic carbon (SOC) in a food forest, redwood forest, pasture, and agricultural field in Dartington, UK, at 0-20 cm and 20-40 cm depths. Similar total SOC was found across all four systems. However, food forest soil showed similar long-term carbon storage to redwood forest, while pasture and agricultural fields stored less.

Janine Voge, Till Newiger-Dous, Emily Ehrlich, Ulrich Ermann, D. Ernst, Dagmar Haase, Isabel Lindemann, Rebecca Thoma, Emilia Wilhelm, Joerg A. Priess, Lukas Egli · International Journal of Agricultural Sustainability · Germany (Leipzig)

This study assessed food loss and waste (FLW) and yields for one year in four Community-Supported Agriculture (CSA) initiatives in the Leipzig area, Germany, comparing them to reference data. Results showed that FLW during production, distribution, and consumption was on average 22–70% lower compared to reference data. Due to lower FLW, CSA initiatives could compensate for yield gaps of 32% on average, reflecting typical yield gaps between organic and conventional agriculture. Co-evaluation with CSA gardeners indicated that FLW could be further reduced at all stages.

Purificación Marín Sanleandro, Ana María Gómez-García, M. Arantzazu Blanco Bernardeau, Juana María Gil-Vázquez, María Asunción Alías-Linares · Forests · Spain

This study in the mid-plain of the Segura River (SE Spain) assessed soil properties and agricultural potential by collecting 68 arable soil samples. Statistical analysis revealed significant differences in organic carbon distribution between calcaric Fluvisols and calcaric Regosols, and among industrial, cultivated, and abandoned soil uses. Cultivated Fluvisols showed a higher average organic carbon content (11.35 g kg−1) compared to abandoned (9.33 g kg−1) and industrial (5.13 g kg−1) uses.

Maraike Probst, María Gómez‐Brandón, Cecilia Herbón, María Teresa Barral, Remigio Paradelo · Applied Soil Ecology · Spain

This study evaluated fungal and bacterial communities in 40 soil samples from 10 urban allotment gardens in Santiago de Compostela, Spain, using DNA sequencing. While microbial richness was comparable to less anthropogenically influenced urban soils, the deterministic effect of soil properties and geographical distances was negligible. Fungal and bacterial communities followed a random distribution and formed very small, often unconnected, microbial association modules, suggesting potential implications of anthropogenic activity for soil health and ecosystem functionality.

Borja Ferrández-Gómez, Juana D. Jordá, Antonio Sánchez‐Sánchez, Mar Cerdán · Sustainability · Europe

A study of nine soils (Technosols) developed over construction debris in Alicante, southeast Spain, analyzing mineralogy, elemental composition and metal availability over two consecutive years, 2019 and 2020. The soils were similar to forest soils in the same area, with no evidence of asbestos clays or excess harmful elements, though DTPA extraction revealed high levels of Mn and Zn in some soils. Organic carbon and DTPA-extracted metal content differed between the two years with no clear relationship observed between them; organic matter content was higher and DTPA-extracted elements were lower in 2019, which the authors attribute to above-average rainfall that year possibly washing away dissolved materials and fine soil particles while promoting natural vegetation growth that increased organic matter and immobilized elements. The study concludes that because metal mobility varies with weather and soil characteristics, and because urban soils develop on materials that require attention despite the benefits of green space, annual monitoring plans for heavy-metal availability are needed, particularly where plants are grown for human consumption, along with controls on vegetables grown in these soils and restricted garden use if problems are found.