Biochar Research Paper Highlights

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Ocean Warming and Ocean Acidification are two representative challenges of Kelp Aquaculture.(Zi-min Hu et al., 2021). Even when propagule supply is not limiting, kelp may fail to establish because of localized abiotic or biotic processes affecting settlement or post settlement survival of recruits.(Morris et. al., 2020).  The Structural complexity of artificial substrates can greatly influence kelp recruitment (Perkol-Finkel et al. 2012), artificial structures could be ecologically engineered (Chapman and Underwood 2011) to incorporate suitable structural complexity.

A potential solution to overcome heat stress effectively while maintaining growth of kelp species is to use a solution of commercial seaweed extracts (biostimulants), to dip juvenile sporophytes before cultivation in the open sea (Umanzor et al., 2019). Alternatively, providing sufficient nitrogen (i.e. NO3−) can help kelp to ameliorate temperature-dependent responses such as growth and photosynthesis, thus enhancing its tolerance and acclimation ability to thermal stress (Fernández et al. 2020).

Algal biomass contains little or no lignin, which enables easy hydrolysis of the biomass for subsequent hydrogen fermentation (Ao Xia a et al., 2015). It is interesting to note that the addition of Biochar in dark fermentation has increased rate and yield of hydrogen production from 26 % and 41 %, (Tianru Lou et al,. 2024) The mechanisms that boost hydrogen in dark fermentation shed light on advantages biochar can provide as a supplemental material for cultivation of kelp gametophytes and sporophytes. Those mechanisms include moderating pH, stimulate the growth of functional microorganisms, moderation of mitigating factors of hydrogen production (biotic and abiotic) and facilitation of electron transfer (Tianru Lou et al,. 2024).

Biochar without post-treatment typically contains only small amounts of nutrients like nitrogen, phosphorous and potassium. Kelp growth requires dissolved Nitrogen in bioavailable forms such as nitrate and ammonium, as well as Phosphorous, Potassium, Calcium, Magnesium, Sulphur, Iron, Iodine, Copper, Boron and Molybdenum (Zhang, et al., 2021).Nutrient impregnation is a common method of improving the effectiveness of biochar as a soil amendment in agriculture, and the same method can be used for kelp cultivation (Osman, et al., 2022).

The critical aspect in question is whether it is more effective to impregnate the biochar with the required bio-stimulants in the hatchery and allowing nutrients to release gradually, or to apply the biochar without impregnation in the marine environment and assess its ability to capture and retain nutrients in the substrate.  A Biochar Aquarium as set up at the Vancouver Island Sea Salt Company and nutrients from the reverse osmosis filters were added to the aquarium and samples of the biochar were taken for subsequent months and the biochar was observed absorbing and retaining marine nutrients.

Surface area and functional group activation

An important consideration is the functional surface area of the biochar. The greater the porosity or surface area, the more nutrients can be retained. The surface area is highly dependent on feedstock and operating conditions, and typically an increase in pyrolysis temperature as well as a high feedstock lignin content is associated with high surface areas. Depending on these factors, biochar can have a surface area of between 20 and 130 m2/g (Tomczyk,  Sokolowska, & Boguta, 2020).

The surface area can be enhanced by methods such as steam activation. This process involves exposing the biochar to high-temperature steam at temperatures between 750˚C and 850˚C and can double the biochar surface area (Shim, Yoo, Ryu, Park, &  Jung, 2015).Whether or not it is necessary to employ post-treatment methods for surface area enhancement will depend on technoeconomic studies encompassing capital and operational costs, as well as the benefit incurred with respect to kelp growth enhancement. The flame cap kiln method requires quenching with water to stop the combustion process so this method of biochar production has the added benefit of introducing introduce steam to the char.

A study on P. hecatensis (pacific red seaweed) demonstrated that treatment  withSargassum horneri extract (Seaweed Extract)can significantly enhance the species thermal tolerance, growth and biochemical resilience under high temperatures, which is especially important as rising seawater temperatures due to climate change threaten seaweed aquaculture (Kim et al.2024).

An important research question to consider is can this seaweed extract pre-treatment mitigation strategy be enhanced using biochar to target  gametophites with seaweed extract? What other kelp and seaweed species respond to this pretreatment, and can the large surface area of biochar provide a reservoir for the seaweed microbiome to augment holobiont recovery from heat stress events.