Nitrogen Reduction, Recycling and Reuse (Environment and Climate Change Committee Report)

Viscount Hanworth Excerpts

Tuesday 6th January 2026 Grand Committee

[Viscount Hanworth (Lab)]

My Lords, the Environment and Climate Change Committee’s report on nitrogen raises many issues, including the effects of nitrogen emissions on the climate, on the air that we breathe and on the water that we drink. However, I shall confine my attention to the role of nitrogen fertilisers in agriculture.

Plants are created largely from air and water. The process of photosynthesis, which occurs in all green plants, combines carbon dioxide, which is present in the air in small quantities, with water, which is essential to all forms of life, in order to create carbohydrates— the structural elements of plants are formed from carbohydrates. The process of photosynthesis, which is powered by sunlight and requires chlorophyll to catalyse it, splits water into hydrogen and oxygen. The oxygen is released into the atmosphere and the hydrogen is combined with carbon dioxide to form sugars and carbohydrates.

Plants require other elements in small quantities for their sustenance. These include phosphorus, potassium, calcium, sulphur, magnesium and iron. More crucially, they require compounds of nitrogen in order to form the amino acids and proteins that are involved in all biological processes, which we may describe as their functional elements. Nitrogen is present in chlorophyll and is contained in the four nitrogen-rich compounds that are the building blocks of DNA—namely, adenine, guanine, thymine and cytosine—but plants cannot obtain their nitrogen directly from the atmosphere. They must absorb it from the ground in the form of nitrogen compounds.

Some of the nitrogen is subducted from the atmosphere when nitric oxide and ammonia are formed by lightning and ultraviolet rays and are washed down by the rain. In a natural environment, this source accounts for approximately 10% of the nitrogen compounds in the soil. The remainder is fixed in the soil as ammonia and nitrates, which are the NO₃ radical, and nitrites, which are the NO₂ radical, by microorganisms that take nitrogen directly from the air.

Some of these nitrogen-fixing organisms are free-living bacteria, whereas others typically live in a symbiotic relationship with certain plants within their roots; leguminous crops are examples of such plants. In their root modules, the bacteria convert free nitrogen into nitrates, which the host plant utilises for its development. In return, the bacteria receive a supply of carbohydrates for their sustenance. When plants die and decay, they release nitrogen compounds that are available for uptake by other plants and crops.

The rapid growth of the population of Britain in the 18th century raised the threat of famine and starvation. After years of stagnation in European agriculture, an agricultural revolution occurred that proceeded in step with the Industrial Revolution, and Britain led the way.

The principal innovation in farming methods concerned the adoption of new crops and a new system of crop rotation. In the Norfolk system, which in fact originated in Holland, a four-field rotation of crops was adopted, which involved the successive planting of wheat, turnips, barley and clover. The effect of the turnips and clover was to enhance the fixation of nitrogen, thereby stimulating the growth of the cereal crops. As the nitrogen supply was improved, other nutrients, particularly phosphorus and potassium, became limiting factors. The only available supply of phosphorus compounds would have been via calcium phosphate from bonemeal.

Additional fertilisation of the soil would have come from farmyard manure and from roughage and litter collected from forests and meadows. By the middle of the 19th century, much of the farmland was already in intensive use and further supplies of foodstuffs could be obtained only by increasing the addition of fertilisers that were exogenous to the farming system. The requirement for fertilisers was met from a variety of sources; these included Peruvian guano, which has its origin in the droppings of sea-birds, of which supplies were virtually exhausted by 1875. Another source of fertilisers was the Atacama Desert, which spans Chile, Bolivia and Peru. When the production of sodium nitrate began in 1804, the nitrates were leached out of the soil by hot water and then purified and dried. The supply reached its peak in maybe 1930. The coking process that is associated with steel-making, which was used to produce town gas for domestic heating and lighting, was a source of ammonium sulphate fertiliser.

Given the increasing demand for nitrates, in view of the rapid depletion of the sources of mineral nitrates, it was inevitable that, at the end of the 19th century, industrial chemists should turn their attention to the business of creating synthetic nitrates. Without some new source of nitrogen fertilisers, there would have been widespread famine within two or three decades. Some intensive research ensued.

The demand was met, eventually, by the Haber-Bosch process, which deploys high temperature and high pressure to synthesise ammonia by combining hydrogen and nitrogen. A successful implementation was achieved in 1908, which was in time to provide Germany with wartime explosives.

Nowadays, the process is the basis for the supply of ammonium nitrate and urea, which are the fertilisers that sustain the worldwide production of food. It has been suggested that, in the absence of these fertilisers, only half the world’s population could be fed and at a starvation level. The combination of nitrate fertilisers, mechanisation, irrigation and the development of high-yield cereals has been responsible, since the 1960s, for what has been described as a green revolution. It is notable that the production of nitrate fertilisers has increased ninefold since the 1960s.

The gains of this revolution are now being lost through farming practices that threaten the fertility of the soil. A significant cause of the declining fertility is the salination of soils that occurs in irrigated lands that are subject to high rates of water evaporation. The salts that are carried by the irrigating waters are liable to be deposited in the soil, to the detriment of the crops. There has also been a massive overuse of nitrate fertilisers that can scorch the seeds of the crops. The rotation of crops that would otherwise serve to restore nutrients to the soil has ceased and been replaced by cereal monocultures sustained by fertilisers and pesticides.

Recent studies show that yields of corn and rice grown on saline soil in the Indus Valley of Pakistan have declined on average by 32% and 48% respectively, compared with the yields of crops grown on non-saline soil. The overuse of nitrate fertilisers is also a feature of agriculture in temperate climates. The effects of the misuse of nitrogen fertilisers are clearly apparent in the United Kingdom. The loose spreading of the fertilisers makes them liable to be washed away. When they reach the rivers, they enrich the water with nutrients that cause excessive growth of algal blooms that block sunlight and deplete dissolved oxygen. This harms and destroys aquatic life.

The availability of chemical fertilisers has encouraged farmers to neglect systems of crop rotation that can be used to maintain the quality of the soils. Farmers neglect to sow cover crops that would restore the nutrients and prevent soil erosion. Ploughed fields are left bare while sterile soil awaits further applications of chemical fertilisers and pesticides. A report from 2019 by the Environment Agency found that, within 60 million hectares of crop-land in England and Wales, almost 40 million hectares of soil are at risk of compaction, over 20 million hectares of soil are at risk of erosion, and intensive agriculture has caused arable soils to lose about 40% to 60% of their organic carbon.

The report of the committee reveals that the UK is lagging behind other European countries in its effort to redress the problems arising out of the intensification of agriculture. A visit to the Netherlands revealed a stark contrast in the relative efficacy of its regulatory systems and those of the UK. The Dutch have made significant progress in limiting the overuse of nitrate fertilisers and in preventing them leaching into water- courses. The report testifies to a confusing mass of UK legislative measures that are overseen by agencies that fail adequately to enforce them.

This state of affairs must surprise anyone who is familiar with the strict controls of farming practices and farm produce that occurred throughout the years of the Second World War and for an equal period thereafter. The Ministry of Food, in conjunction with the Ministry of Agriculture and Fisheries, exercised considerable control over farm production and farming methods. Such control was gradually ceded in post-war years under Conservative Governments. The lack of effective regulation and guidance of agriculture in the UK has been an inevitable accompaniment of the decline of the Civil Service during the periods of Conservative Governments. One is reminded of the period from 2014 to 2016 when Liz Truss was Secretary of State at the Department for Environment, Food and Rural Affairs. During that time, she was an advocate of all manner of unreasoned acts of deregulation.

I believe that the problems besetting agriculture in the UK need to be addressed by a reconstituted department of agriculture that would be active in imposing regulations and offering firm guidance to farmers.