The decarbonization case for this pathway cannot be built without a reliable supply of low-cost biomass and better understanding of the impacts on livestock performance, which requires resolving the production consistency, and impact testing gaps addressed in this subsection.

Species Selection and Cultivation

Scaling Asparagopsis cultivation to commercially relevant volumes will be technically demanding

To provide seaweed as a feed additive (~0.5% inclusion rate) to the US current livestock industry would require an estimated 1.5-1.7 million metric tons of dry seaweed, which would currently be 25% of all seaweed produced globally (adapted from Vijn et al., 2020). While several companies are looking to address it, scaling and standardizing the cultivation of Asparagopsis will be a challenge. More research is needed to identify the ideal cultivars that possess both the efficacy and safety required of additives as well as the ability to scale.

Non-Asparagopsis species with methane-inhibiting properties have not been adequately researched

 Given the challenges in cultivating Asparagopsis, other seaweed species need to be researched for suitability in different locations. Early results are promising for the use of sugar kelp (Saccharina latissima) for example, but more research is needed.

The relationship between cultivation process parameters and final product quality is poorly understood

Location, season, strain, processing method, all affect the bromoform content and stability of finished products, but the interactions between these variables are not systematically characterized. This makes quality control difficult and undermines the reproducibility of efficacy trial results.

Environmental impacts of large-scale seaweed cultivation are not well understood

Both ocean and land-based seaweed cultivation could have local environmental impacts including marine mammal entanglement (ocean based), spread of diseases and invasive species introduction (land and ocean based). There could also be improvements to the environment from carbon sequestration and water quality and habitat improvements. Trials to study these impacts at appropriate scale need to be conducted.

Product Delivery to Livestock

Long-term efficacy and effects on animal health are largely untested

 While there have been several tests on the efficacy of Asparagopsis on methane emissions and productivity of sheep and cattle, studies on the long term efficacy of these additives have been limited and indicate that efficacy may wane over time. (Vijn et al., 2020) Longer-term animal trials that last a complete production cycle (for beef cattle that means 12 months from weaning though to slaughter and for dairy cows, it means at least one full lactation cycle of approximately 305 days) would help to evaluate the long term effects of selected seaweed species/strains on productivity, health, product quality, digestibility of nutrients, active compound residues in manure, and manure greenhouse gas emissions

Knowledge of the rumen microbiome and the impact of seaweed additives need to be expanded

Knowledge of the microbiome and its contribution to animal health is still in its infancy. Metagenomic studies are imperative to understanding how certain seaweed species/strains impact the rumen microbiome and whether these effects could be manipulated to benefit animal health and productivity, as well as the environment (Vijn et al., 2020).

The gaps identified in this section reflect the challenges in processing seaweed to make the final product consistently and with low lifecycle emissions since these together determine the cost per unit of emissions avoided that sets the floor for commercial viability.

Land-based cultivation methods have significant unresolved engineering challenges

Many challenges are present in the development of land-based cultivation methods. For example, in the use of photobioreactors to grow seaweed, issues such as non-uniform light penetration and circulation could impact productivity.

Processing of Seaweed into Livestock Methane Inhibitors

Stability of bioactive compounds during processing is a critical bottleneck, and current methods are insufficiently characterized

Methods to dewater seaweed and process them into feed additives result in the loss of volatile bioactive compounds such as bromoform. Optimizing these methods to minimize loss of bioactive compounds and reducing the concentration of iodine and heavy metals is a key need (Liu et al., 2023).

Processing seaweed can be energy intensive, significantly impacting lifecycle emissions

Thomas et al. (2025) found that freeze-drying Asparagopsis taxiformis under current conditions offsets enteric methane savings entirely. Processing accounts for the majority of lifecycle emissions in current supply chains, driven primarily by the energy demands of freeze-drying. Lower-emissions alternatives (oil extraction, proprietary methods, barn drying) exist but have not been systematically compared at relevant scale against standardized LCA methodologies.

Product Delivery to Livestock

Challenges to deliver feed supplements to pasture systems need to be overcome

Delivering feed supplements is difficult in pasture-based systems, where cattle graze with minimal human interventions in their food supply. However, these systems account for ~70% of enteric methane emissions, and so delivery mechanisms such as boluses, mineral blocks, water troughs  and self-feeders need to be tested for efficacy.

Methane Measurement Technologies

Tools to measure methane emissions from cattle are expensive and not widely available

The primary tool available (GreenFeed Pasture System) measures twenty cattle per day, costs ~$100,000 and can be found only at a handful of research institutions. This reduces access both to cattle producers and researchers, slowing down research and development as well as the development of carbon markets. We need to develop affordable and accurate measurement tools to accelerate the development of solutions.

This section summarizes gaps that need to be solved for adoption at scale and therefore for decarbonization impact with cultivation costs and unresolved safety concerns being the chief among them.

Seaweed cultivation costs are high relative to the market value of the supplement product

Producers need to identify other high-value co-products (e.g., nutraceuticals, pharmaceuticals, pigments, fertilizers, biofuels) which can be consistently extracted from Asparagopsis biomass through a biorefinery approach and other approaches to diversify revenue streams and improve the overall economic viability beyond just methane mitigation.

Safety concerns about bromoform as a potential carcinogen create market and regulatory risk

The US EPA classifies bromoform as a potential carcinogen due to the incidence of intestinal tumors in female rats. While research suggests that there are negligible risks to humans (Cressey et al., 2025), absence of conclusive evidence could hamper consumer adoption.

Private investors are hesitant to invest in large scale projects that carry science risk

Given the need for research and prior failures in areas such as algae biofuels, investors are hesitant to invest in large scale projects.

The gaps below reflect the fact that seaweed-based methane inhibitors cannot achieve the adoption rates needed for meaningful aggregate emission reductions while users and communities remain skeptical about the value of the products.

Coastal seaweed operations often have a negative perception among landowners and other users of nearby waters

Seaweed farming sometimes face negative perceptions from other users concerned with the enjoyment of coastal areas and views (Rector et al., 2025).

Farmer skepticism about benefits of the seaweed product needs to be addressed

Even if regulations mandate the use of seaweed or other products to reduce methane emissions, farmers’ willingness might be limited unless there are co-benefits such as increase in animal performance (e.g., improved productivity, efficiency, health, or product quality). Farmers also express skepticism about the link between methane emissions and climate change (Reyes et al., 2023).

Regulatory frameworks are inconsistent across the world and slows down investment

While Asparagopsis based feed additives are approved in Australia, Europe has different policies for whole seaweed (approved) vs. extracts (not yet approved). The path to approval in the United States is expected to be around ten years. Delays and obstacles to getting permits result in uncertainty and discourage investment and expansion.

Absence of a robust carbon market or legislative mandates to reduce agricultural emissions reduces rate of adoption

Without carbon credits for enteric methane reduction or legislative mandates requiring adoption of methane-reducing practices, producers face a cost premium for seaweed supplements with no offsetting revenue.