by Selim E. on Mon, 5th, Nov 2018
The moment when the engine stops, the yacht heels and silently starts plowing through waves has ever been a magic moment for me. The fact that a ship can be moved by the sole power of wind still fascinates me from a technical point of view. And I must admit, I often argue for my hobby by pointing out that sailing is an environmentally friendly activity.
However, recent developments with regard to plastic pollution and yacht disposal encouraged me to take a deeper look at the environmental impact of yachting activities. I am aware that the pure announcement “to take a deeper look at the environmental impact of sailing” will make some colleague sailors sigh and refrain from reading on. Yet, I think it will be helpful to reveal some facts about the environmental impact of our beloved hobby. And I promise, I will try to do this is an objective way, just to provide you with knowledge to make your own decisions.
The goal of the following analysis is to raise awareness about the environmental impact of yachting among yachtsmen in general, but is especially addressed at charter skippers and crew. The scope of the analysis is limited to the sailing activity and related activities, such as crew travel. The environment of a sailing activity is the air and water that surrounds a boat and the organisms that live in this environment. The whole analysis is based upon a practical example which may sound familiar to the most of us.
Emissions from one week sailing trip and a rough estimate of their quantity in kg ((C) Selim E.) Example
A crew of six goes for a sailing trip in the Adriatic sea in the area of Murter Island. Five of the six mates live in Vienna in Austria. The sixth lives in Salzburg. The five Viennese manage to go together with one car (a mini van), The guy from Salzburg travels with his own car (a station wagon type of car). The whole crew embarks on a 42 feet sail yacht from a local charter company. They start their trip the day after their arrival and sail about 250 nautical miles. They sleep onboard and eat their dishes partly on board partly on land in restaurants. They anchor their ship three times, the other four nights they stay in marinas. In total they use the boat’s built-in diesel engine for 10 hours and consume 30 liters of diesel. Their dinghy is used for several landfalls and they use around 3 liters of gasoline for it.
Impact on air quality
The main impact on air quality is caused by the travel activity necessary to arrive at the yacht. Sailing in a narrow sense has no negative impact on air quality. However, in a broader sense a sailing yacht needs an engine for berthing in harbors and anchoring activities. Bad wind conditions might require as well to start the engine from time to time which leads to emissions of different kind. A sailing crew often uses a dinghy with an outboard engine to make landfall. A sailing yacht usually is equipped with a propane gas fueled oven which affects air quality as well during operation. In this article I calculate CO2 emissions only.
CO2 emissions in numbers from a one week sailing trip Based on the example above, a one-week sailing trip emits approximately 650kg of carbon dioxide (CO2). About 85% of the CO2 emitted is caused by the car travel of the crew. Only around 13% is caused by boat and dinghy operation during the week. The oven is responsible for only 0.23% of CO2 emissions. Exact numbers are shown in illustration 2.
CO2 emissions per source from a one week sailing trip Now I will compare the numbers with other travel options and some reference values. In case the crew decides to travel by airplane the emissions are at least two times higher (~1480kg). The CO2 emissions caused by travel to and from boat then accounts for 94% of the total. Even worse is a scenario where the crew opts for a 42ft motor yacht powered by two 250hp engines. An assumed consumption of 80 liters per hour will lead to an almost 5 times higher CO2 emission (~3140kg). The boat then is accountable for 82% of CO2 emissions. From these comparisons one can see that distance to sailing locations is making the difference. If you live somewhere near to the sea you will have a minor impact compared to somebody who needs to travel a long distance by airplane or car.
Different sailing scenarios and their CO2 emissions In relation to the average CO2 emission of an Austrian per year, the above sailing trip accounts for around 10%. Given a recommendation from climate experts the CO2 emission budget for a person to stabilize climate change should be reduced to 1.6 tons per year. Enjoying a sailing trip in a remote destination, there will be not much CO2 emission budget left to spend for other things or a second sailing trip ;-)
CO2 emissions from a sailing boat are not a direct threat to environment and marine life in particular, but contribute as well to global warming in the long term and acidification of sea water. NOx and particle emissions from Diesel engine are not included in this analysis.
Impact on water quality and marine life
Human excreta
During a week of sailing the crew produces about 8.5kg of human feces and about 84 liters of urine. In Croatia, like in many other countries, the so called “black water” goes directly into the sea water or is pumped first into an intermediate tank and released later into the open sea.
The impact on sea water has been investigated in several scientific studies. Accordingly, high concentrations of fecal bacteria and their direct impact on fauna and flora can be seen mainly in enclosed coastal areas like harbors and bays. The impact is twofold as human excreta like other biotic waste on the one hand decomposes and on the other hand serves as a nutrient for other organisms. Decomposition uses up oxygen from the surrounding water and if it is too much, fish and other aquatic animals and plants will lack oxygen and may die.
High levels of nutrients as a result of discharged human excreta in enclosed areas may lead to uncontrolled algal and plant growth. As a consequence algal blooms reduce light penetration in water and may produce toxins which as well may lead to extinction of marine animals. When algae decompose they cause as well oxygen depletion.
A recent study of large harbors in the Adriatic sea shows that concentration of bacteria stemming from human excreta is about 20 times higher than in surrounding coastal waters and around 30 (Coli bacteria) to 130 (Enterococci) times higher than what WHO says is sufficient water quality for safe bathing. Although only partly responsible for increased fecal bacteria in commercial harbors, recreational vessels and their crews are contributing a large part in bays used as anchorages.
Dish washing sewage
Based on personal experience I assume 40 milligram of soap used for personal cleaning per day and person and 420 milligram for dish washing for the whole week. This amounts for 2.1 liters of soap used during the trip. Luckily, a quite recent scientific report shows that soap and detergents have no adverse impact on the aquatic or sediment environments at current levels of use.
Anti-fouling coatings
Hull paints that continuously release one or more biocides (scientific word for poison) have been the preferred method of fouling prevention on yachts for more than a century. By intention, biocides in these so called antifouling paints are toxic and can have a negative environmental impact if the biocide does not quickly degrade after release and maintains its toxicity and bioavailability.
The sailing yacht used in the example above measures around 12 meters in length (waterline) and 3.9m in width and has a draft of 2.4m. For the area exposed to seawater I assume around 40m2 of wetted surface. Assuming that a copper based anti-fouling paint was used, the yacht releases around 12g of copper into sea water during one week.
As mentioned above, the steady release of copper from hull painting is intentional. Copper in high concentrations has a toxic effect on various marine organisms. Impact on marine life has been scientifically investigated in several studies. Results show that copper concentrations above natural levels deteriorate filtration rates of several mussel species, impair settlement of coral larvae and growth rate of particular algae species.
Increased rates of copper in the enclosed coastal areas with increased boating activity have been reported by several scientific studies. A clear relation between antifouling and increased copper concentration has been observed for example in Australian anchor sites and European ports for recreational boating. In these studies concentration of copper has been found to exceed national guidelines for environmental and health safety. In particular cases copper concentrations are about 10 times higher than allowed values. In the United States several states have already banned copper-based antifouling paints for recreational yachts.
Micro and macro plastic
Modern yachts are increasingly made of plastic. Sailors increasingly dress themselves in performance clothing made of plastic fabrics. Sailors use plastic bottles, cups, bags, straws and other packaging onboard which often find their way into the sea.
Plastic bottle caps found at a beach in Brioni National Park Running parts like sheets and halyards are made of plastics like Polyester, Polyethylene, Polyamide and Nylon often known by their brand names Dacron, Dyneema, Twaron etc. These parts are the parts that are susceptible to increased wear off. Wear off of these parts are the fibres that they are made of. In particular, these are microfibres released during operation of ropes.
To date no studies exist that explored the abrasion behavior of marine ropes. Realistic estimates for microplastic wear off from rope handling is therefore not possible. Kumar and colleagues found that a Nylon area of around 1cm² in size looses around 0.2 grams for a load of 0.5 kg (5N) and 500m pull distance which equals 0.18 cm³ of volume. In general, the wear off can be assumed very low as ropes in general do not slide for a long distance around blocks or edges under high loads.
Plastic made packaging frequently used on board is in fact a larger problem. Plastic bottles and bags easily get overboard and due to their floating characteristic accumulate at shore and ground. Over time, macroplastics – due to UV exposure and abrasion - breaks up in small parts.
The so called microplastics is increasingly found in seawater, seafloor sediments and in marine animals. Research on the effects of microplastics is at its beginnings. However, first studies show that it negatively affects growth rates of various marine organisms. A major concern is that microplastic does not biodegrade and needs around two hundred years to degrade in seawater. The pace in which plastic is accumulated in the oceans today is alarming. Scientific studies have found plastic in a wide variety of marine animals that are used for food production. Recently, an international study has found microplastics in human stool from independent individuals around the world.
Noise
Main sources for noise in a recreational yacht are the engine, the ships movement through water and the sonar. Each of these sources emits different sounds. The characteristics of the sounds depends largely on the size, design and location of the engine, and the yacht’s size and construction.
Small boats like the yacht from the example above usually have a Diesel engine emitting sounds with a frequency below 300 Hz. But several studies have found that noises from propeller may as well cause frequencies around 100kHz. A typical sonar system of a yacht emits sound signals with a frequency from 50 - 200kHz.
Many marine animals are able to hear and interpret underwater sounds of different frequencies. For example, marine mammals like dolphins and whales use sound signals for communication and echolocation of prey. Bottle nose dolphins use frequencies ranging from 75 to 150,000 Hz. This range overlaps for example with yacht sonars and may therefore disturb their echolocation systems used for hunting. In general, studies have found that underwater noise causes stress to different marine species. Thus, leading to increased energy demand and disturbance during feeding or migration activities. Several species of whales have been reported to loose their orientation capabilities and subsequently have been found trapped in bays and other shallow waters.
Summary
The environmental impact of a one-week sailing trip can be considered low compared to other recreational activities. However, considering the whole lot of sailing trips during a year the environmental impact is huge. Especially in the Adriatic sea the number of sailing activities has increased during the last decades. Recent statistical data shows that in Croatia 215,000 recreational yachts are registered in harbors. A similar number can be expected in Italy. Given these data, one can easily calculate the overall impact of sailing activities.
A source of trouble are long-term impacts of sailing activities. Just to give an example, almost half of the carbon dioxide emitted from the sailing activity is dissolved in sea water in the long term, as is with the far larger amounts CO2 from other sources. The dissolution of carbon dioxide leads to an increase in hydrogen ion concentration in the ocean (acidification) of sea water. In the last 100 years, since industrial revolution, concentration of hydrogen ions has increased by 30%. Some marine organisms, that rely on calcium carbonate structures such as corals and some plankton are vulnerable to dissolution due to increased levels of acid in sea water.
Disposal of yachts is going to be a challenge in the near future. (Foto Selim E.) An example for indirect impact of sailing activity is increased land use. Land use is as a consequence of marina construction and other sailing related infrastructure. Another example of indirect impact is the yacht disposal. To date its is not clear how glass or carbon fiber reinforced hulls can be recycled. The major problem is the composite structure of resin and glass fibers. An increased number of yachts has reached its end of life and must be disposed soon. In Europe an estimated 25,000 yachts are expected to be disposed in the near future. Necessary capacities for disposal are currently not existing. Yacht owners need to charge around 1,800 EUR for a 12m yacht. Experts assume that many yacht owners will leave their yacht in harbors or anchorages or dispose it in the open sea.
What can we do to reduce our impact?
Depending on the source of impact yachtsmen may take different types of action to reduce their impact. Here are some suggestions.
- Travel to and from the yacht is a major source of carbon dioxide emissions. As a crew, team up to travel with a single car or reduce equipment weight. Often it is not necessary to travel too far for having a sailing experience.
- When sailing, use your sails instead of the engine. This requires a different style of sailing from target driven sailing to wind driven sailing. However, it is extremely satisfying when you learn to play with the winds. Ask yourself, if you really need an engine for your dinghy. The dinghy engine is not a safety equipment, it is just for convenience when going ashore. It is usually sufficient to use oars instead.
- Ask for holding tanks for black water. This will allow you to dispose black water and gray water later through a professional service on land or in the open sea beyond three miles from shoreline. This is another easily applicable action to reduce negative impacts on marine life, especially in enclosed marine areas like anchorages and harbors. The areas that we want to enjoy, unspilled. Many charter companies have yachts that have holding tanks, but it is often necessary to ask explicitly for it.
- Avoid plastic littering of the sea. First, try to avoid plastic packaging. For example, when buying food supplies take paper bags instead of plastic bags or even better, use reusable cotton bags. As a skipper ask your crew to not! dispose plastic things in the ocean (accidentally or not). As a crew you may plan a beach cleaning activity in a beach of your choice. This is a fun activity, that your crew will feel great about. Whenever you sea plastic things floating in the water collect them and bring them on board. It is kind of a man-over-board training and your crew will have fun.
- There is not much you can do about the biocides dissolving from anti-fouling paints. But you may ask as well the charter company which kind of anti-fouling they use. This will raise awareness of this problem among charter companies and if many ask, they will have to respond.
- Anchoring causes damage to sea bottoms and the marine life inhabiting it. Avoid anchorages if there are for example mooring buoys. Reduce anchor chain to the safety minimum and consider to use a shore line to avoid swinging.
Let’s keep our seas clean!
There has been a vivid discussion on this article on the legendary
cruiser's forum.
Sources
Carbon dioxide
Human excreta
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Sewage
Anti-fouling coatings
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Plastics
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Noise
- Noise from ships and boats
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