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Nitrogen oxide (NOx) and carbon dioxide (CO2) pollution are the greenhouse gases that are two of the most important pollution issues facing humanity today

The Primary Pollutants

Carbon dioxide (CO2) produced by burning fossil fuels for heat, transportation and manufacturing upset the normal balance of the earth's CO2 causing increasing temperature of Earth. Excess carbon dioxide isn't only affecting the atmosphere. It has also made the oceans 30 percent more acidic, affecting a wide variety of sea organisms. CO2 becomes a poisonous gas when there is too much of it in the air we breathe. Carbon dioxide poisoning can lead to central nervous system damage and respiratory deterioration in humans and other breathing creatures.


Nitrogen Oxides (NOx) are odorless colorless products of internal combustion diesel engines. Pollution occurs when nitrogen oxides are released as a gas into the atmosphere during the high temperature combustion of fossil fuels.  NOx is a primary driver of ocean acidification that is destroying fish stocks and sensitive ecosystems. NOx is also a chief culprit in urban smog with serious human health issues with over 3 million deaths reported from resultant respiratory issues.  In Europe marine transport emissions have been identified as the #1 source of pollution especially in geographically confined regions like the Baltic. Diesel vehicles and trucks are being banned from European cities and it is expected that port cities will soon begin regulating NOx emissions of boats in their harbors.


The World Health Organization (WHO) estimates that over 3 million people die  and countless millions have compromised respiratory problems due to toxic marine diesel engine emissions. There are approximately 4 million diesel-powered boats in the world less than 200' long with new boats being built every day. The diesel motors on these boats currently have no viable system to reduce NOx or CO2 emissions. Unlike other diesel gas emissions, a large percentage of harmful gases stay low in the troposphere damaging people’s lungs. Nitrogen oxide alone is considered a bigger health hazard than secondhand smoke from cigarettes. In addition, maritime transport worldwide is responsible for about 2.5% of global greenhouse gas emissions annually.

As a response to massive health issues
created bydiesel engines the

International Maritime Organization has mandated
that as of December 31, 2020 all new vessels over 78ft/24m must reduce
NOx emissions 80%

While the new IMO regulations are a positive step in controlling NOx emissions in NEW vessels there are no provisions, at this time, to regulate NOx or CO2 emissions in the millions of existing vessels on the water today. However, there are serious efforts by the European Union and regional governments to impose strict NOx emissions regulations on Tier IV 130 KW/177hp diesel engines.

Greenhouse Gases Emissions from Boats:
Marine vessels emit 40 times more greenhouse gases than cars and trucks on the road today

Unlike automobiles, trucks and construction equipment that have government mandated regulations controlling exhaust emissions, 98% of marine vessels under 200ft/60m have zero pollution abatement equipment installed on their respective diesel engines. Yet, in just the US alone, over 2 billion gallons of diesel fuel are burned in boats annually. For every gallon of diesel fuel burned by marine craft over 9 pounds of nitric oxide (NOx) are emitted into the air and water. This documented fact equates to over 100 million tons of dangerous NOx produced by boats annually in the USA marine sector based on 2018 statistics. When all the international Marine vessels from ferries, commercial craft and recreational boats that use diesel engines are included the pollution statistics are staggering. NOx is an odorless and invisible poison gas that has been totally ignored by the marine industry and international governmental agencies throughout the world.


In order to fully understand the complexity of equipping boats and marine related craft with satisfactory pollution abatement equipment the unique problems and evolutionary development of marine engine overboard exhaust must be understood.


1- Boat engines and generators are located in a confined non-airflow locations and rely on seawater to cool the heat generated by the engines and exhaust systems.

2- The seawater is continually pumped through an engine heat exchanger to maintain proper engine temperature and also cools the hot engine exhaust gas before it is discharged along with exhaust gas back into the water.

3- Engine rooms in boats are surrounded with other vital and heat sensitive equipment and components such as electronic engine controls, batteries, navigation electronics and electrical wiring.

heat exchange.jpg

Approximately, 90% of all the boats worldwide use this type of “wet exhaust” system shown in the diagram (left), including engines that turn electric generators. The cooling seawater is  pumped through the engine and mixed with the engine exhaust and pumped back into the air and water without exhaust treatment

Many commercial fishing vessels, tour boats, ferries and ships use a “dry exhaust” system. Simply put, the engine cooling radiator is built right into the hull and exposed to cool seawater. “Keel cooling” does preclude mixing the seawater with exhaust gas. However the untreated raw engine exhaust gas is simply piped up through an exhaust stack into the atmosphere.

Why we need the
STec RCI compact exhaust treatment system now.
 One of the best kept secrets is the massive negative effects of unregulated
marine diesel exhaust emissions.
emmissions chart.JPG

The unique physics of thermal combustion power creates an accelerant or multiplier where one gallon of diesel fuel that weighs 7.1 pounds burned in a diesel engine creates an astounding 21 pounds of carbon dioxide (CO2) and 9 pounds of nitrogen oxides (NOx). CO2 is the primary greenhouse gas responsible for global warming, and in 2016 reached a level in the earth’s atmosphere of over 400 PPM (parts per million) for the first time in the last 800,000 years.  Walt Schulz, a marine engineer for over 4 decades, realized early that raw, untreated diesel exhaust caused by marinized, seawater-cooled engines contribute to greenhouse gas pollution.

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