There is a need for better characterization of seaweed biomass composition, specifically the complex polysaccharides (e.g., fucoidan, carrageenan)

This robust characterization and understanding of the variability by species, cultivation processes and harvest time is necessary to support the development of sustainable conversion and extraction pathways and ensuring product consistency (Laurens et al., 2020).

This section summarizes processing and engineering gaps that need to be solved for multi-product biorefineries to have climate impact- they range from developing scaled manufacturing to improving storage and developing suitable extraction processes.

A major gap exists between demonstrated pilot scale and commercial reality

No seaweed biorefinery has been demonstrated operating with a production capacity greater than 5 tons ww per day. The transition to commercial scale is hampered by the complexity of integrating multiple processes inherent in cascading biorefineries. These processes must be fully integrated and demonstrated through extended multi-season operations.

There is an unresolved tradeoff between process simplicity and value extraction.

It is still not clear how much conversion efficiency, yield, or product recovery can be sacrificed in order to achieve a biorefinery system that is simple enough to scale, flexible across seaweed types, and commercially practical. Comparative process studies coupled with technoeconomic analysis are needed to resolve these knowledge gaps.

Handling the high-water content of freshly harvested seaweed is a massive challenge for refining economics and environmental impact

Drying is a costly and energy-intensive process (Milledge et al., 2020) which significantly contributes to high operational expenditure (OPEX) and the carbon footprint of the overall value chain. Recent life cycle analysis synthesis work finds that drying and energy-intensive extraction account for 50–70% of total global warming potential in seaweed biorefineries (Chaurasiya et al., 2026). Optimizing of thermal drying as well as the study and optimization of alternative dewatering methods such as screw press dewatering aided by washing is required (Dussan et al., 2023). Another possible approach is the development of saltwater-based processing methods (Jones et al., 2020).

Seaweed’s high ash content is a major challenge for conversion processes and for economic impact

The dry mass of seaweeds contains 12–46% ash depending on species, creating processing problems across every pathway. In pyrolysis specifically, alkali and alkaline earth metals in the ash act as catalysts that promote unwanted cracking reactions, reducing bio-oil yield and quality (Choi et al, 2014) and causing slagging and corrosion in reactors.

More knowledge on ensiling (storage of seaweed by fermentation usually with lactic acid) is required in order to use this technique for long-term stabilization of biomass in biorefineries

In places where the processing of wet biomass is not an issue, ensiling can sidestep the challenges with drying seaweed preserving bioactive compounds until they need to be used. However, it has not been implemented at scale and there is limited knowledge of interaction with downstream refining processes (Milledge et al., 2020).

Cascading biorefinery processes for seaweed biomass typically rely on acid or alkaline treatments and organic solvents (e.g. for lipid or pigment extraction) that are incompatible with food-grade certification and can have environmental impacts if not suitably managed

Enzymes play a critical role in more sustainably breaking down polysaccharides from terrestrial biomass into simple sugars for further processing.  However, these commercially available enzymes do not work as effectively on seaweed components and so seaweed-specific enzymes need to be developed. Furthermore, the development of halotolerant enzymes (enzymes that have good activity in seawater) will reduce the need for drying and the use of freshwater to clean the seaweed (Johnston et al., 2023). These enzymes are currently in proof-of-concept studies and their development for use in industrial settings will reduce energy consumption, minimize solvent usage, and preserve the biological activity of the target compounds.

This section summarizes gaps that need to be solved to increase investments in biorefineries so that they can scale for climate impact- these range from better data to make decisions to increasing supply of feedstock for biorefineries.

The high capital expenditure (CAPEX) required to establish integrated cascading biorefinery setups poses a major techno-economic barrier

Techno-economic analysis (TEA) coupled with life cycle assessment (LCA), underpinned by process simulation, will be needed to compare biorefinery configurations across key variables including number of extraction steps, product portfolio, and equipment specification, with the aim of identifying configurations that meet defined thresholds for profitability and climate impact while minimizing CAPEX.

The lack of reliable long-term supply of fresh feedstock represents a significant operating risk for biorefineries

Supply chains need to provide reliable feedstock in sufficient volume to sustain industrial-scale operations.

There is a lack of standardized, comparable Life cycle analysis (LCA) and technoeconomic analysis (TEA) data

There is a general lack of good quality, comparable data from LCA and TEA studies against which to assess and validate results, which is a big issue, given the goals of cascading biorefineries to balance for climate and economic impact.

For biorefineries to scale and have impact, the economic value generated must be shared with the communities where they are built- this section summarizes these gaps.

The public perception regarding seaweed utilization is not being sufficiently measured

Efforts are required to develop social license as production volumes scale up, which merits developing a methodology and process to measure social perception of biorefineries (Dussan et al., 2023).

There is a need to ensure that the economic benefits generated by complex, high value biorefining are passed on to the seaweed farmers and local coastal communities

Currently, many farmers are price-takers due to their dependence on buyers, given that they often rely on middlemen called aggregators to whom they sell fresh or dried for a low price.

 Development of the industry must prioritize inclusive business models that include education and skill development for local communities, ensuring the creation of local and decent jobs

Opportunities and training programs must be established locally to allow communities to own and operate micro-biorefineries and capture a greater share of the value added from cultivation to product development.

This section summarizes policy gaps that need to be solved for biorefineries to be developed to include seaweed-based products for decarbonization with the absence of policy mechanisms to stimulate the expansion of markets being key among them.

Absence of Policy Incentives and Market Stimulation Mechanisms

Very few demand-side policy tools exist to grow markets for climate-mitigating seaweed products. Government procurement programs, which have historically played a decisive role in scaling nascent industries, are largely absent in the seaweed-based products for decarbonization sector. Without demand created through public purchasing commitments, offtake agreements or blending mandates (for biofuels), companies find it difficult to justify the capital expenditure required for biorefinery development.

Failure to Value Ecosystem Services in Policy Frameworks

Seaweed cultivation delivers a range of ecosystem services beyond the direct commercial value of the biomass itself, including nitrogen and phosphorus removal from coastal waters, and the provision of habitat for marine species. However, existing policy and regulatory frameworks largely fail to recognize, quantify, or monetize these co-benefits. The absence of ecosystem service markets means that biorefineries cannot capture revenue streams that would otherwise significantly improve project economics.

Cost Disadvantage of Seaweed-Derived Products Relative to Incumbents

Products derived from seaweed, including biofuels and bioplastics, currently face a cost disadvantage relative to their fossil-fuel-derived counterparts. This disadvantage reflects both the early-stage nature of the industry, and the failure of market prices to reflect the full environmental costs of incumbent products. Policy mechanisms such as carbon pricing and extended producer responsibility schemes can level the competitive playing field by either raising the effective cost of high-carbon alternatives or directly supporting the unit economics of seaweed-based products.