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Post on / Nikolas Hagemann -Ithaka

Use of biochar application in hops

A key goal of the NET–Fuels project is the utilization of residual and otherwise un-used biomass, e.g., from the food industry, in the TCR (Thermo-Catalytic Reforming) process.

Hops are an important specialty crop in certain regions of Germany, with the Hallertau region being the largest and best known. In the past, the whole hop cone was used for brewing, but currently especially large breweries optimize the taste and their processes by using hop extract that contains the ingredient of interest, namely the alpha acids. After extraction, pellets made from hops are a potential feedstock for the TCR process that we included in the project as an agricultural residue. Fraunhofer processed these pellets from hops extract residue on the TCR30 (Thermo-Catalytic Reforming with a 30 kg per hour throughput). To achieve a circularity and recycling of nutrients and carbon, Ithaka applied the resulting biochar in a hops garden. The goal is to promote the growth of hops whilst additionally improving the soil in the long-term as a means of climate change adaptation.

Figure 1: Left and center: Hops garden after concentrated application of biochar and fertilizer prior to covering the ground shoots with soil. Right: Hops garden with ground shoots being covered with soil.

"The goal is to promote the growth of hops whilst additionally improving the soil in the long-term as a means of climate change adaptation"

Hops is a perennial crop with both a deep (up to 4 m) root system. Additionally, there are shallow summer roots that are formed when young shoots on the ground are covered with soil as part of standard practice. This promotes the growth of the bines where the cones are formed. Just like most specialty crops, the cultivation of hops is subject to considerable challenges induced by climate change. Fungal diseases occur more frequently, and droughts in early summer make mineral fertilization less efficient, as the nutrients applied are not dissolved and thus not transported to the roots. In addition to these specific challenges, soil improvement and build-up of soil organic matter is generally desirable.

We tested the following modes of biochar application, each at a dose of 2 t / ha (tonne per hectare), which equates to 1 kg per plant:
•   Concentrated broadcasting of biochar and fertilizer just before covering the shoots on the ground with soil
•   Injection of biochar with compressed air and water into the root system of the hops
•   Injection of biochar and dissolved fertilizer

Standard practice of fertilization (broadcasting), concentrated broadcasting of fertilizer, injection of water and injection of dissolved fertilizer served as controls. We used a Vogt Geo Injector fluid that was modified for the injection of a biochar suspension. We will evaluate both quantity and quality of the harvest to judge if hops-derived TCR char can increase sustainability and climate change adaptation in this cropping system.

Figure 2: Injection of water, biochar and/or fertilizer between the hops plants

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