Nutrient credit trading: a way to curb nitrogen and phosphorus pollution and the expansion of oceanic dead zones

By Faye Palmer, GLOBUS Correspondent

What are dead zones?

Dead zones are anoxic areas of water that cannot sustain biodiversity. They occur naturally, but there is increasing concern that anthropogenic activities are accelerating their growth. Nitrogen and phosphorus fertilizers are primarily responsible for dead zone expansion as they cause eutrophication – they overload the water with nutrients. Due to increased nutrient loads, there is accelerated and excessive plant growth on the surface of the ocean which blocks out vital sunlight and oxygen. Subsequent anoxic waters make aquatic survival impossible, disrupting food webs and ecosystems.

Causes and effects of dead zones

The primary cause of dead zones is nitrogen and phosphorus pollution from agricultural fertilizers and industrial sewage. These nutrients enter the ocean after seeping into rivers and streams. The planetary boundary for nitrogen (the amount of nitrogen our planet can sustain) is defined as 62Tg/year, however anthropogenic activity produces approximately 227Tg/year. This suggests that we have exceeded the planetary boundary and are now at high-risk of disrupting the system. Indeed, excessive use of nitrogen and phosphorus fertilizer causes eutrophication which leads to huge algae blooms covering the water surface and suffocating marine organisms underneath.

This leads to the degradation of vital ecosystem services. Anoxic waters make aquatic survival impossible, therefore reducing supporting ecosystem services as marine habitats are lost, leading to a loss of functional and genetic biodiversity. This has subsequent impacts on regulatory processes as food webs are disrupted, which causes imbalances in the marine ecosystem. Implications for provisionary services are inevitable – for example, fish stocks required for commercial fishing will be greatly reduced.

Importance to Human Development Agenda

Fertilizer contributes to food security and poverty alleviation, which are essential sustainable development goals. So we cannot simply stop using fertilisers: level of agricultural activity in 1900 shows extremely limited use of fertilizer and could only feed 2.4 billion people. Thus, we must develop a strategy that increases global food security whilst minimising environmental impacts and the expansion of oceanic dead zones.

Figure 1: Graph to show positive correlation between dead zone expansion and fertilizer consumption (from: )

Nutrient Trader Application

In order to facilitate nutrient trading, I propose the creation of a new, innovative application called the Nutrient Trader app. 

Here, National governments would set monthly nutrient pollution quotas to point-source polluters, farmers, and public/private industries. This information would be displayed on their app profiles with usage data shown, to allow for efficient monitoring.

Sources who reduce their monthly nutrient pollution below quota targets earn credits: for every 10kg of nitrogen or phosphorus saved, they would receive 1 credit, which they can then sell on the app in exchange for money. Those who exceed their quota, or want to exceed it next month, must buy credits. These transactions would all be facilitated by the app, which is efficient, secure and easy for governments to monitor.

How does it work?

The average amount of nitrogen applied per hectare of farmed land2 from fertilizers from manufactured and organic fertilizers is 110 kg/ha and 9kg/ha respectively. If a farmer uses precision farming techniques to reduce nitrogen pollution by 20%, they earn 22 credits/ha. If they have 100 hectares, that’s 2200 credits. On the app, they will be rewarded by the government with 2200 credits which they can sell to another farm, who perhaps can’t yet afford precision farming techniques. If 1 credit is received for every 10kg of nitrogen, this farm could now produce an additional 220kg of nitrogen above their original quota.

General rules

Only nitrogen or phosphorus can be traded for comparable credits (e.g., nitrogen for nitrogen). Nutrients are measured in kilograms/year. 1 credit = 10 kilograms of nitrogen or phosphorus. Credits only last one year – the total number of credits earned resets after this duration. 

Sources who want to reduce their pollution but do not possess the financial capital for costly upgrades can apply for government investment via the app. Instead of simply purchasing credits and continue polluting, sources can apply for government investment through the app and begin earning credits which will contribute to their profit and growth. This encourages small businesses to get involved, thus making it more accessible to a wider range of sources. Indeed, this rests on government willingness and capability to invest in their environment, however it is hoped that with pressure from the UNEP and the integration of nitrogen-phosphorus pollution into the SDGs, worldwide governments will be persuaded to take action.

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