In a pivotal phase of the H2OPE development initiative, SEM conducted rigorous ‘large-scale’ testing of the technologies process in order to analyse the nutritional composition of the fertiliser produced at the end of the treatment train.
For the purpose of the trial, machinery was supplied from our key equipment partners who were also present on-site during testing to offer support and insights for optimal operation. Digestate, sourced from a local biogas plant, was passed through the machinery which had been engineered to process at a rate of up to 4m3 per hour.
Despite the fact the plant wasn’t fully automated or controlled by a computer, the different stages mimicked the key steps, including dewatering and nutrient transfer, of a commercial grade H2OPE system. During this testing phase, SEM took charge of the thermal stage, employing thermal dehydrators to advance the H2OPE process.
The digestate was passed through the machinery and yielded approximately 1 tonne of nutrient-rich solid matter. This material underwent pelletisation in a test mill and was followed by tests for composition and structure. The pellets were ozone-treated for preservation, stored in sealed plastic bags at room temperature and regularly checked for quality.
The pellets underwent thorough analysis, including internal assessments and testing by a third-party laboratory. Critical parameters such as tensile strength, compressive strength, density, and bulk density met industry standards for handling and applying standard fertiliser pellets.
The composition data in Table 1 and Table 2 (seen below) revealed impressive nitrogen (N) levels, approximately three times higher than typical organic fertilisers. Pellets from the raw material boasted a total nitrogen content of around 17%, while pellets with added mineral N approached the targeted level of 20% within a 2.5% range.
Although phosphorous (P) and potassium (K) levels in the produced pellets were relatively low at around 1.3% and 0.4%, respectively, they align with many organic fertilisers. These levels result from the initially low P and K content of the digestate, which can be easily increased through strategic methods such as using an organic sorbent and mineral addition.
While this narrative has primarily focused on the pellet production, the separated water phase from the process also underwent detailed analysis tailored to final water polishing specifications.
In summary, the large-scale testing of H2OPE revealed promising advancements. The meticulous analysis of the fertiliser production process, from the usage of large-scale equipment to the pelletisation and preservation of H2OPE pellets, has demonstrated the scalability and efficacy of the technology. The next phase of the trial involves actively involving our customers to obtain their digestate, facilitating the processing of more material. This collaborative effort aims to contribute to the finalisation of the design for the H2OPE process.
As we conclude this phase of development, the findings not only highlight the potential of H2OPE to revolutionise sustainable agriculture but also pave the way for further optimisation and broader implementation on a commercial scale.