Due to the large acreage of olive trees in the Mediterranean basin, the biochar from olive tree pruning may become an important resource as part of circular economy strategies. However, so far, there is not much knowledge on whether the same characteristics are repeated in biochar once production is up-scaled to an industrial level. Accordingly, this study aimed to scale up the production of olive tree pruning biochar with three reactors (semi-pilot, pilot and industrial) to ascertain the production parameters that determine the characteristics of the obtained biochar and its possible toxicity to use in agriculture or environmental applications. First, the production conditions in the semi-pilot reactor were optimised by testing three temperatures (400, 500 and 600 °C), with the result that 600 °C was the optimal production temperature because of a high carbon content (70.88%), moderate pH (8.1), good carbon sink (R50 > 0.5) and low contents of PAHs (<6 mg/kg) and heavy metals, resulting in a phytostimulanting effect for all the crops studied. Then, the production was upscaled, using 600 °C as pyrolysing temperature. At the industrial scale, accurate temperature control is essential because when temperatures above 650 °C were reached, the biochar showed a pH above 11, resulting in severe phytotoxicity. The longer retention time of the material in the industrial pyrolysers improved the carbon stability and, therefore, the biochar’s role as a carbon sink. Consequently, it was proven that it is possible to produce olive tree pruning biochar adequate for agriculture and environmental applications with large-scale equipment, and the two most important factors needing control are the temperature and retention time.

Doped compost consists of compost inoculated with Bacillus siamensis SCFB3-1 that is formulated in biochar and then mixed with the compost. The study objective was to analyze, at field scale, the effect of doped compost on the melon and pepper yield and on the soil microbiome, hypothesizing that the synergy between the components of doped compost confers additional benefits to the crop. Two doses of compost (2 and 5 t/ha) and two doses of the inoculant (biochar+SCFB3-1) with respect to the compost (3% and 6% w:w) were tested. The highest yield was observed for a reduced dose of mineral fertilization (NPK -20%) with a compost dose of 2 t/ha with 6% of the inoculant. Specifically, the yield increase compared with the control, which only received NPK, was a 47% increase in melon and 28% in pepper. The microbiome of the bulk soil was not modified by the doped compost, but the composition of the rhizosphere microbiome changed, increasing in the abundance of Bacillus (the inoculated strain), but also changing the relative abundance of other genera in the bacterial community. Future works will be focused on unravelling the possible effects of phytohormones on the observed results.

Treated bio-residues can be used as biostimulants in crops within the circular economy approach to reduce the use of traditional fertilisers. In this work, we optimised the combination rates for three types of treated bio-residues (compost, biochar, and anaerobic digestate (AD)) in two microcosm trials, one with a combination of compost and biochar and other with biochar and AD. The crop used was maize, and the variables analysed were plant growth, and soil chemical and biological properties. The combination of bio-residues improved plant growth and soil biological activity to a greater extent than one product alone; that is, compost and biochar performed better than compost alone and biochar, and AD performed better than biochar alone. However, while the concentration in the plant biomass of several essential nutrients for crops increased in the treatments with compost and biochar, and with biochar and AD, compared to the untreated controls, the nitrogen concentration was reduced. This was due to the competition for nitrogen between the plant and the soil microbiome, whose activity was activated. Due to the importance of nitrogen in plant growth, the increase in biomass production could be explained not only by the higher availability of other nutrients but also by the plant-growth-promoting activity exerted by the more active soil microbiome. Further research should focus on validating this hypothesis and unravelling the mechanisms involved. From the environmental site, the presence of biochar in the mixtures of organic residues reduced the soil nitrogen at risk of lixiviation and sequestered carbon, which partially compensated for the increased CO₂ emissions because labile forms of carbon were present in the remaining organic residues.

The production of mineral fertilisers relies heavily on mineral deposits that are becoming depleted or is based on processes that are highly energy demanding. In this context, and in line with the circular economy and the European Green Deal, the recovery of nitrogen (N), phosphorus (P), and potassium (K) from organic wastes using chemical technologies is an important strategy to produce secondary raw materials for incorporation into mineral fertilisers, partially replacing the traditional sources of N, P, and K. However, there are very few studies on the agronomic and environmental effects of such substitution. The aim of this work was to evaluate plant growth under microcosm conditions and the effect on the soil microbiome of mineral fertilisers in which part of the N, P, or K content comes from bio-based materials (BBMFs), namely ash, struvite, and a patented chemical process. The crop was maize, and a metataxonomic approach was used to assess the effect on the soil microbiome. The BBMF treatments were compared with a control treated with a conventional mineral fertiliser. The conventional fertiliser performed significantly better than the bio-based fertilisers in terms of maize biomass production at the first sampling point 60 days after sowing (DAS), but at the last sampling point, 90 DAS, the BBMFs showed comparable or even better biomass production than the conventional one. This suggests that BBMFs may have a slightly slower nutrient release rate. The use of fertiliser, whether conventional or BBMF, resulted in a significant increase in microbiome biodiversity (Shannon index), while it did not affect species richness. Interestingly, the use of fertilisers modulated the composition of the bacterial community, increasing the abundance of beneficial bacterial taxa considered to be plant-growth-promoting bacteria, without significant differences between the conventional mineral fertilisers and the BBMFs. The predominance of PGPRs in the rhizosphere of crops when BBMFs are used could be part of the reason why BBMFs perform similarly or even better than conventional fertilisers, even if the rate of nutrient release is slower. This hypothesis will be tested in future field trials. Thus, BBMFs are an interesting option to make the food chain more sustainable.

Globularia alypum L. (Plantaginaceae) is widespread in the Mediterranean region and traditionally used against diabetes, digestive disorders, infections, and skin problems. This review summarizes its botanical features, ethnobotanical uses, phytochemistry, pharmacological effects, and toxicological profile. Relevant studies published between 1991 and 2024 were retrieved from Web of Science, Scopus, PubMed, and other relevant databases using targeted keywords in English and French. Extracts of G. alypum have shown significant antidiabetic, antioxidant, anticancer, antibacterial, anti-inflammatory, anticoagulant, nephroprotective, and wound-healing activities in vitro and in vivo, which were largely attributed to its diverse secondary metabolites such as phenolics, flavonoids, and iridoids. Toxicological studies indicate generally low risk at tested doses. However, further research is needed to elucidate the molecular mechanisms underlying these activities, validate its efficacy through clinical trials, and evaluate long-term safety, thereby bridging traditional knowledge with modern pharmacological evidence.