This section summarizes the science gaps ranging from lack of tailored species selection for construction application to information on public health impacts to solve for to ensure that seaweed-based construction materials can have climate impact at scale.

Cultivation Techniques and Scale-up

Species selection for construction applications is underexplored relative to other seaweed markets

Construction applications span a wide range of required material properties. Systematic screening of species against relevant functional criteria could identify candidate species beyond the current Sargassum dominated landscape. Another factor in species selection is the need for low-cost scalable biomass.

Public health

There is insufficient information on the effect of seaweed construction materials on human health

Construction products using seaweed materials (like Sargablocks and Sargacreto) require further studies to test the environment around such constructions for Sick Building Syndrome, indoor air quality, acoustics, and radiation. The inherent properties of whole seaweed materials, such as their tendency to absorb water, make them prone to rotting in high humidity environments, limiting the scope of their use, particularly as insulation.

This section summarizes gaps that need to be solved for decarbonization because seaweed’s inherent physical properties (water absorption, chloride content, and susceptibility to rot) limit its scope as a widespread construction material until optimized processing addresses these challenges and standard performance testing establishes the process parameters that deliver consistent structural outcomes.

Processing and conversion technologies

There is limited understanding of product performance based on standard tests

Apart from a few examples such as MDF and Sargablocks, there is limited information on product performance over time as well as an understanding of the process parameters that impact product performance.

Processing and conversion technologies are not optimized for optimal product performance

There are very few real-world studies that have looked at a “design of experiments” approach to optimize performance of construction materials by varying process parameters.

Seaweeds have several difficult-to-manage properties that need to be managed for product performance

Seaweed’s properties, such as its tendency to absorb water and alter its shape and weight, can be difficult to work with in construction. In addition, the high natural salt (chloride) content of marine algae must be mitigated, as retaining high chloride levels is unsuitable for construction, causing long-term degradation and corrosion of adjacent steel reinforcement. In humid environments, whole seaweeds are also prone to rotting. To make seaweed a suitable exterior material, it is important to find a way to create hydrophobic films that can withstand different weather conditions. (World Bank, 2023

This section summarizes gaps that need to be solved to scale for climate impact, ranging from production costs to inadequate life cycle assessments.

High production costs and technological limitations currently impede competitive market entry

The primary economic barrier is the overwhelming dominance of established building material systems (synthetic insulation, concrete) which are highly efficient and benefit from economies of scale. Seaweed-based materials are not cost-competitive with traditional alternatives, with cultivated temperate brown kelp (wet weight) costing $400–$500 per ton at the farm gate, compared to less than $125/ton for cement/concrete blocks in the EU. (The World Bank Group, Global Seaweed New and Emerging Markets Report, 2023).

There is not enough seaweed to prompt interest from the construction industry

Interest in seaweed as a construction material from incumbent industry players will require high volumes of biomass. In areas relying on wild-collected materials, such as the Caribbean Sargassum influx, the unpredictability of how much biomass will arrive each year creates logistical challenges for industrial-scale valorization.

Low awareness of seaweed-based material options limits demand even where willingness to pay exists

There are consumers that are willing to pay a premium for more sustainable products and brands that cater to them, but they are less familiar with seaweed materials as compared to alternatives such as sustainably sourced wood.

Limited demand for green buildings which reduces use of finite resources

There needs to be more demand for green buildings, particularly those that discourage the use of resources such as land-based biomass that competes with food cultivation. That would allow seaweed-based construction materials to enter the market.

Lack of clear economic incentives is a barrier to capital investments

Some regions (e.g., Caribbean) could leverage seaweed-based construction applications to deal with invasive algae blooms, but it is a burdensome investment for small regional investors and operators. This could be mitigated with concerted global financial efforts to stimulate exploration and application.

There aren’t sufficient high quality life cycle assessments to prompt interest from regulators to support the use of low embodied carbon construction materials from seaweed

There is a necessity to quantify the emissions impact from the cultivation, processing operations as well as end of life in construction applications. Given the early stage of the industry, limited data exists to make projections for life cycle emissions at commercial scale.

This section summarizes the policy and governance gaps that need to be solved for climate impact including the lack of product acceptance protocols.

There are no standardized product acceptance protocols for bio-based alternatives in general and seaweed-based materials in particular

The existing lack of established industry standards for sustainable building practices makes it difficult for contractors to choose materials.

Testing and Acceptance of new products is an onerous and expensive process

New materials including new seaweed-based materials used particularly in critical structural applications must undergo compliance testing and certifications (such as structural or thermal testing), which require financial support and longer project timelines, slowing adoption.