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Duckweed, the UK needs it.

As the UK’s drought continues and the Maize for winter feed withers in the fields we need an alterative. Our farmers are already feeding winter food to their livestock. There is an option and it is called Duckweed. That green stuff floating in our ditches and rhynes. It may well provide the alterative to farmers having to cull their livestock or buy in expensive food, if they can find it?

Even if the rain comes now, August 2026, the loss of crops will still create feed shortage through the winter. With wetter warmer winters Duckweed may be the best hope to create the feed the farmers need.

Duckweed production provides: speed, protein, and simplicity.

  • Rapid growth — Duckweed can double its biomass in 24–48 hours under optimal conditions. That’s faster than soy, rye grass, alfalfa, or most forage crops.
  • High protein content — Depending on species, protein ranges from 25–45%, comparable to soy meal.
  • Low resource demand — It grows on shallow water with minimal inputs, making it ideal for marginal land or integrated farm systems.
  • Environmental benefits — It absorbs nitrogen and phosphorus, helping clean agricultural run-off.

For UK farmers facing tight margins and environmental regulation, this combination is compelling alongside the cost of deployment on fields too dry to cultivate and plant.

An existing setup

Scalable

It has been done before at scale. One of the most notable large‑scale experiments happened in the 1980s–1990s, when Nestlé supported duckweed cultivation systems in parts of South America, especially in Peru and Colombia.

Here’s what that system looked like:

  • Integrated lagoons — Farmers built shallow ponds fed by nutrient‑rich water from livestock or food‑processing waste streams. These can be simple plastic channels laid on the ground
  • Continuous harvesting — Duckweed was skimmed daily, dried, and mixed into feed for pigs, poultry, and fish.
  • Circular nutrient flow — Wastewater fed the duckweed; duckweed fed the animals; animals produced manure that fed the lagoons.
  • Low‑tech, high‑yield — The system required minimal machinery, making it accessible to smallholders.

Results: Farmers reported improved feed efficiency, reduced reliance on imported feed, and cleaner water leaving the farms. Nestlé’s interest was tied to stabilising local supply chains and improving sustainability metrics long before ESG became mainstream.

The UK can borrow heavily from this model — but with modern upgrades. The author has since 2015 been involved in providing project vision and supporting the design of Duckweed schemes in Peru, Jordon, South Sudan , India and other countries with water and food poverty.


Why Duckweed Fits the UK’s Agricultural Landscape

The UK has several structural advantages that make duckweed adoption easier than in many countries:

  • Abundant rainfall → consistent water availability for ponds. Our warmer wet winters deliver that water.
  • High livestock density → steady nutrient streams for duckweed growth.
  • Pressure to reduce soy imports → duckweed offers a domestic alternative.
  • Strong research institutions → ideal for optimising strains and systems including Brymore Academy.
  • Contractors and farmers able to install the systems quickly and efficiently.
  • No Effluent

Duckweed can be integrated into:

  • Mixed farms — where nutrient flows are already diverse.
  • Dairy farms — using slurry lagoons as growth beds.
  • Poultry operations — replacing part of soy meal.
  • Aquaculture — especially trout and carp systems.

How do you produce Duckweed?

at the most basic level a channel/ raceway with a water containing nutrients being being forced around a channel with Duckweed growing on the surface. 25% is harvested every day.

The plan shows a typical closed circulating raceway,

Growing medium can be water with added nutrients or effluent containing nutrients that duckweed will clean as part of the duckweed production process.

How do you feed livestock with Duckweed?

  • collect it daily,
  • a quick wash, using water you have already cleaned.
  • press to remove free water and it can be fed wet directly to livestock.
  • No complicated machinery and what equipment is needed can be fabricated by a competent local fabricator.

Duckweed will clean water

Duckweed is a fast-growing aquatic plant that naturally purifies water by absorbing excess nutrients, heavy metals, and other pollutants, making it an effective and sustainable water-cleaning solution.

It can clean effluent. Be used as sewage treatment plant because it converts nutrients to high protein biomass.

Mechanisms of Water Purification

Duckweed, belonging to the Lemnaceae family, cleans water primarily through phytoremediation, where it absorbs contaminants directly from the water column. It rapidly takes up nitrogen and phosphorus, which are major contributors to algal blooms and eutrophication, effectively reducing these nutrients by up to 63–65% in wastewater over a few weeks earthecobalance.com+2. The plant also absorbs ammonia, heavy metals, boron, and organic chemicals, helping to protect aquatic life and improve water quality earthecobalance.com+2.

Physical and Ecological Benefits

Duckweed forms dense mats on the water surface, which block sunlight and suppress algae growth, improving water clarity and oxygen levels biologyinsights.com+1. Its small root systems stabilise water, reduce turbulence, and allow suspended solids to settle, further enhancing purification biologyinsights.com. By trapping pollutants in its biomass, duckweed acts like a natural sponge, though regular harvesting is necessary to prevent re-release of stored contaminants earthecobalance.com.

Applications

Duckweed is used in wastewater treatment systems, agricultural ponds, and small-scale fish farms, offering a low-cost, environmentally friendly alternative to chemical treatments. It can remove up to 84% of chemical oxygen demand (COD), 87% of total nitrogen, and 85% of total phosphorus in controlled studies, demonstrating its effectiveness in both municipal and rural settings impress-he.eu. Additionally, harvested duckweed biomass can be repurposed as fertiliser, animal feed, or even human food, adding value to its water-cleaning role earthecobalance.com+1.

Summary

Duckweed is a multifunctional, sustainable solution for water purification. Its rapid growth, nutrient absorption, and pollutant-trapping abilities make it ideal for improving water quality in ponds, rivers, lakes, and wastewater systems, while also providing ecological and economic benefits earthecobalance.com+3.

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Chilton Trinity and Pawlett Hams

The EA’s 2011 document Managing flood risk on the Severn Estuary provided the EA’s vision for Steart Peninsula  including what subsequently became the Steart Marshes salt marsh  scheme.

Pawlett Hams no longer protected after 2030

Under present plans six  years after the completion of the proposed Bridgwater Tidal Barrier Pawlett Hams will cease to be defended. That means that the river banks will no  longer be maintained and the process of handing more farmland back to the sea  will start again. The estuary will in time return to the state it was in more than 500 years ago before the levels were drained. According to the EA this will see 387 Ha or just under 1000 acres of farmland lost to food production and the local economy although only 47Ha  is actually required to make up for coastline squeeze.

The Parrett Estuary Flood Risk Management Strategy   (PEFRMS) is a document remarkable for its narrow  vision that is more interested in extending the habitat for birds  whilst  completely failing to understand or chooses to stay silent on the impact of saltwater on agricultural land. The only economic impact considered seems  to be tourism.

Parrett Flood Management Recommended Strategy

Section 2.1.6 (b) notes that

North Devon and Somerset Shoreline Management Plan (Hartland Point to Anchor Head), Halcrow, due 2010. We are concurring with their emerging policies.

As such much of the real detail  is provided in the EA’s Shoreline Management Plan rather than the overarching Parrett Estuary Flood Management Strategy which is a long term plan to let down the flood defences along the River Parrett allowing the sea up to the edge of Chilton Trinity and trading off land in Sedgemoor for economic development elsewhere around the Severn Estuary. It is a step back in time with individual communities afforded  long term term flood protection rather than comprehensive  flood defence.  The high level strategy  for the PEFRMS is provided below  following on is information from the shoreline management plan and recently available information for the preferential flooding of farmland as part of the Bridgwater Tidal Barrier Scheme.

Pawlett Hams Realignment is the complete loss of Pawlett Hams as can be seen from the key plan in the Parrett Estuary Flood Management Strategy  and noted in item c above.

Applicable Shoreline Management Plan delivery of the Strategy that includes the loss of 387 Hectares (1000 Acres of land) at Pawlett Hams is  reproduced below.

Parrett Estuary (Combwich to River Brue) Policies 7d38 to 7d42

Individual policies for various  sections of the River Parrett and adjacent land are listed below. 7d39 is  worth noting as it has the next major realignment of the flood defences after Pawlett Hams allowing the River Parrett to come up within 1000m of the village of Chilton Trinity.

Policies 7d38 to 7d42

Full copies of the EA policies can be found at

Steart Peninsula (Stolford to Combwich) 7d34 to 7d37

Parrett Estuary (Combwich to River Brue) 7d38 to 7d42

Timescales 

all documents refer to timescales and these are

  • Short Term (to 2025)
  • Medium Term (to 2055)
  • Long Term  (to 2105)

Chilton Trinity

South of the Parrett the EA ultimately proposed to let the marshes return to the very edge of Bridgwater  whilst Sedgemoor District Council  and the EA’s Bridgwater Barrier team have left a space at site 4 for a bridge that is on the way to a planned inter tidal area  and represents the expansion of the Steart Peninsula scheme  up to Bridgwater.

EA presentation Severn Estuary Forum 2017

Managed Realignment

the planned retreat of the existing flood defences

Policy 7d42 Flood defences from Dunball To the River Brue

Policy 7d39 Combwich to Bridgwater (Parrett west) managed realignment.

Those two policies when implemented will along with Steart Marshes and the Bristol Ports land transform the Parrett Estuary.  There will be no new link possible between West and East Somerset.

Future (long term) Inter tidal habitat – salt marsh and mud flats

Total agricultural  land lost to agricultural will be around 5000 acres. There is a certain irony that the EA policies will in reducing UK agricultural land export food production abroad and potentially increase famine oversees.

In the short term  the  proposed secondary flood defences  shown below are required because the EA will not keep  raising the banks above the present levels. sea level rise will continue and the frequency of seawater flooding will increase. The route of the secondary flood defence is not dissimilar to the future managed realignment above.

Secondary Flood Banks based on Bridgwater Tidal Barrier at Site 5

The gap in the flood defences at Walpole still left open for floodwater to flood the area as it previously did in the 80’s

After the planned completion of the Bridgwater Tidal Barrier  a 1:200 flood is expected by the designers to flood land to the north of Chilton Trinity with saltwater. The maps below represent some of the 50 maps prepared by the BTB designers to support the decision on location of the BTB barrier; the complete set of maps can be found on the SDC Strategic Flood Risk Assessment page.

The maps below show the impact of the river banks not being raised to match rising sea levels apart from  the protected communities. The end result is the preferential flooding of farmland with saltwater during certain tide and storm conditions as presented during the Severn Estuary Forum 2017   held in Bridgwater.

None of this information was presented during the two EA/SDC public consultations in 2016. 

2025 1:200 Flood Return

The map below shows one of  breach locations modelled. A breach can occur anywhere, the map does not say its saline (salt) flood waters escaping from the river. They are merely designed to provide an idea of the  likely consequence of it happening. The full pack of maps shows a number of breach locations and these are yet to published by Sedgemoor District Council.

River Bank fails at Dunball at land to the north of Chilton Trinity flooded

One of the maps produced by the designer showing the safety risks associated with their present scheme.

BRIDGWATER TIDAL BARRIER ; SITE 5; FLOOD HAZARD 1 :1000 YEAR FLOOD EVENT