As global temperatures rise, the need for sustainability becomes more urgent. Reducing reliance on fossil fuels and other CO2 emitting energy sources is critical, making a shift to renewable alternatives such as offshore wind power essential. This study examines offshore wind farms in the North Sea, an area that presents both significant opportunities and challenges for a wide range of stakeholders. While the potential benefits are clear, the development of offshore wind farms is a complex undertaking and companies are continuously working on innovative solutions to improve their implementation. In particular, this thesis focuses on curtailment of offshore wind farms in the North Sea.

Curtailment means halting the operation of offshore wind turbines entirely or reducing the speed to a maximum of two rotations per minute. Curtailment is initiated when negative energy prices occur. Initially, it may appear that negative energy prices are not a significant issue. However, they are generally disadvantageous to consumers due to their disruptive effect on market balance. Furthermore, curtailment is initiated for the sake of grid stability. When there is a surplus of energy, grid instability occurs. This should be prevented to prevent power outages. Most importantly, when curtailment is initiated, bird mortalities are prevented. When offshore wind turbines halt their operation entirely or reduce the speed to a maximum of two rotations per minute, birds do not collide with offshore wind turbine blades, therefore preventing bird mortalities.

Curtailment in the Netherlands is initiated during nights of migration periods in Autumn and Spring, when a threshold of 500 birds per kilometre per hour are migrating. The way this works is that virtual kilometres are studied using bird radars, when 500 birds or more cross this virtual line in an hour, this implies mass migration. There is a downside of curtailing for the sake of offshore wind farms for the sake of preventing bird mortalities. If energy demand is not met due to the absence of the wind energy because of curtailment, gas-fired power plants are compensating this loss of energy. The gas-fired power plants use natural gas to produce energy. Gas fired power plants consequently emit CO2. This implies that the Netherlands is willing to prevent bird mortalities while emitting CO2. This raises the following ethical issue and main research question: When, if ever, is curtailment ethically acceptable in offshore wind farms in the North Sea?

To answer this ethical research question, different ethical approached are studied, two in particular, consequentialism and non-consequentialism. Utilitarianism is derived from consequentialism, which is an ethical theory that focuses on the consequences of the actions taken. Non-consequentialism theories, in which the consequences of the actions taken are not all that matters, but places greater emphasis on the actions taken than on the consequences of those actions. In the field of ethics, it is not possible to satisfy both consequentialist and
non-consequentialist perspectives simultaneously. Consequently, a choice must be made between the two. This thesis accepts a consequentialist approach and therefore rejects the non-consequentialist approach. The primary reason for this choice is that, according to consequentialist theories, there is a greater moral obligation to prevent suffering than according to non-consequentialist theories.

The consequences of curtailment for the sake of preventing bird mortalities is emitting CO2. Emitting CO2 affects both the environment and humans. This thesis focuses mainly on the consequences of these additional CO2 emissions for humans. In this thesis the framework of Disability-adjusted Life Years (DALYs) is used. One DALY is the equivalent of one healthy year of a person’s life lost. DALYs consist of Years of Life Lost (YLLs) and Years Lived with a Disability (YLD). Additional CO2 emissions result in DALYs of human beings. In other words, by preventing bird mortalities the Netherlands are willing to emit CO2, which eventually leads to the loss of a human life.

To derive exact amounts, a hypothetical curtailment scenario is assessed. The hypothetical curtailment scenario uses the offshore wind farm ‘Borssele’, real-life data and secondary data to derive exact amounts of the consequences of curtailment. Exact amounts include bird migration fluxes, number of bird mortalities prevented, amount of additional tons of CO2 emissions, the monetary costs of additional tons of CO2, the amount of DALYs per emitted ton of CO2, the cost of one DALY, the amount of DALYs per hypothetical curtailment scenario and
the amount of curtailment scenarios lead to the loss of one entire human life.

The offshore wind farm Borselle, with its 173 offshore wind turbines, are tested using three bird migration fluxes: the current threshold of 500 birds kilometre per hour, twice the threshold namely 1,000 birds kilometre per hour, and real-life data from the night of October 19/20 2022 of 1,386 birds kilometre per hour. The conclusion of these different bird migration fluxes is that for the bird migration flux of 500 birds per kilometre per hour, one human life is lost while 7,110 bird mortalities are prevented. For the bird migration flux of 1,000 birds per kilometre per hour, one human life is lost while 14,220 bird mortalities are prevented. And for the real-life data bird migration flux of 1,386 birds per kilometre per hour, one human life is lost while 19,710 bird mortalities are prevented. One human life is lost due to the fact that additional CO2 emissions result in DALYs.

The question arises why or why not, people ought to be indifferent between a number of bird lives and one human life, thus a trolley problem arises. A trolley problem is an ethical thought experiment in which a decision must be made regarding the trajectory of a trolley on either Track A or Track B. The decision is made by pulling a lever, which determines the path of the trolley. In a trolley problem, individuals, animals, or other entities are situated on both tracks. The individuals, animals, or other entities on the track the trolley is headed to are killed,
whereas those on the other track are spared. This means that in this trolley problem, people ought to choose between a human life, or a number of bird lives, depending on the threshold of the bird migration flux.

If the objective is to preserve human life, the curtailment of offshore wind farms is never justified when additional CO2 is required to meet energy demand. Indeed, this would imply that saving any animal, even if it entails the emission of the slightest amount of CO2 emissions, would be considered ethically unjustifiable. Consequently, animal-friendly facilities such as wildlife crossings, artificial birdhouses, bee hotels or fencing for wildlife protection are deemed unjustifiable as manufacturing facilities, given that such facilities emit CO2 as a by-product of their production process.

Another framework used to determine whether or not to be indifferent between the life of a human being and a number of animals, is welfare ranges. The ‘Moral Weight Project’ obtained welfare ranges for 11 farmed animal species. A welfare range is a spectrum in which a human or an animal can feel pleasures and pains. Assuming that welfare is not exclusively important for humans but rather for all entities, it can be determined how much welfare an exact number of animals could achieve compared to one human being. The framework of the Moral Weight Project ought people to be indifferent between one human being and 19 birds. This would imply that the threshold of the bird migration flux ought to be decreased to 1.4 birds per kilometre per hour. If this is the right course of action, the Netherlands ought to curtail every single night during Autumn and Spring. This view is rejected in this thesis as this implies that offshore wind farms ought to curtail at a very low threshold.

Another way to determine welfare ranges for birds is by looking at the number of neurons in bird’s brains compared to neurons of a human being. A reason to use neurons to derive a welfare range is as more neurons in a brain means greater cognitive capacity, meaning that a certain number of neurons is needed in order to be capable of complex thinking. Comparing the number of neurons of birds to the number of neurons humans have, lowers the welfare range for birds significantly compared to the Moral Weight Project. This changes the indifference ratio of one human being and 19 birds, to one human being and 3,019 birds.

It should be acknowledged that, given the ethical focus of this thesis, some readers may not agree with the theories and assumptions presented. In this study, certain assumptions will be made, although people may have alternative perspectives. This report does not aim to provide a comprehensive response to the assumptions. Although some theories and assumptions will be subjected to criticism, in certain instances, the assumptions made are the most probable estimates, given the inherent uncertainties.