Carbon emissions and the 2-stroke ZEV (zero emission vehicle)

Zero Emission 2 stroke
2 stroke Zero Emission Vehicles are a reality now

Carbon emissions and the 2-stroke ZEV (zero emission vehicle)

If you are concerned about climate change, or you are a fan of 2 stroke engines, this could be the most important article you will ever read.


We clarify the issues with carbon emissions, global warming, biofuel, zero emission vehicles and legislation and correct misconceptions about 2 stroke motors.


More importantly, we join the dots between technologies to provide a clear path to reduce carbon emissions.  Quite simply, the best option to reduce carbon emissions is to bring back 2 stroke engines.


We understand that perception is strongly weighted against 2 stroke motors, so we step through the many reasons why these engines are the best option to combat climate change. At each step, we provide links to research papers and government statistics to enable you to verify our logic.

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Carbon emissions, zero emissions vehicles and global warming

The end goal of reducing carbon emissions is to slow the rate of global warming

It seems to be a straight forward goal, but legislation is working against this goal in many cases. We will return to this phrase as jargon makes it easy for us to lose focus on the end goal of REDUCED CARBON EMISSIONS

Raise the subject of global warming and a confused mess of solutions come forward: Zero emission vehicles, reduced hydrocarbons, reduced carbon emissions, electric vehicles, and biofuels are all pushed as having the same purpose.  Unfortunately, many ‘solutions’ are increasing global warming rather than reducing it.

Legislation has been written to address perceptions rather than to provide proper guidance.  Policies have outlawed what is perceived to be causing the problem rather than trying to define any clear path to reduce global warming.

Some of the following may seem a little basic, however, if we want to reduce global warming, we have to clarify these buzzwords and how greenhouse gasses, ZEVs, biofuels, and carbon emissions, affect climate change.

Carbon emissions pollution
Understanding carbon emissions and greenhouse gasses

What are greenhouse gasses?

The second largest, and most problematic, greenhouse gas is Carbon Dioxide (CO2). This is the most important greenhouse gas as human activity has the greatest influence on this gas.

The largest greenhouse gas is water vapor (H2O). The warmer our planet becomes, the more water vapor is held in the atmosphere.
Hydrocarbon pollution
Hydrocarbon pollution
Other greenhouse gasses are methane (CH4), carbon monoxide (CO), nitrous oxide (N2O) and Ozone (O3).  Although these are potent greenhouse gases, they are produced in far smaller quantities than CO2 and have far less influence on global warming.

Greenhouse gas emissions

Greenhouse gas emissions are added to the atmosphere by burning fossil fuels such as natural gas, diesel, coal or gasoline. 1/3 of the world’s increase in CO2 is produced by transport (cars, buses, trains and bikes). The increase in greenhouse gas is believed to increase global warming.

Large amounts of greenhouse gas is also produced by rotting vegetation. Gas from rotting vegetation does not, however, add to the greenhouse effect as plants remove greenhouse gas from the atmosphere as they grow. Decaying plants simply return the CO2 absorbed while growing.  Rotting vegetation is, therefore, carbon neutral.
CO2 emissions
CO2 is carbon emission

What are carbon emissions?

Carbon emissions are the production of Carbon Dioxide (CO2) gasses. Greenhouse gas is a slightly wider term that can include non carbon based gasses such as Ozone and water vapor. 


Man made greenhouse gasses and carbon emission both refer to the production of CO2

pThe production of Methane and Carbon Monoxide are also both carbon emissions and greenhouse gasses.  As Carbon Dioxide is the major greenhouse gas, the term carbon emissions usually refers to CO2.


This carbon emissions calculator will help you understand what portions of your lifestyle are contributing to carbon emissions.

How do carbon emissions lead to global warming?

When greenhouse gas is added to air, it has an insulating effect which holds more of the heat that would normally radiate into space. 

It is believed that adding greenhouse gasses through burning fossil fuels is the cause of global warming.

Carbon emissions from electric power station
Carbon emissions from electric power station

Carbon emissions in the United States

  • 28% of carbon emissions in the United States are produced by cars, buses, trains and trucks.

  • For the average family, the largest contributor to carbon emissions in the United States is the household car.

  • In the US, an average car produces more than 5 tons of carbon emissions every year.

  • Electricity is the second largest contributor to carbon emissions in the United States. On average, the home creates 24% of the total household emissions. The main contributors are electrical appliances and gas/oil for heating. The average US home produces 12 tons of greenhouse gas per year.

  • 60.3% of electricity in the US is from coal, gas and oil power stations which contributes to carbon emissions. 19.7% of electricity is generated from nuclear reactors and 19.8% is renewable (wind solar etc.).

  • America emits more carbon than any other nation. The average person in the US produces 16 tons of greenhouse gas every year.  This is 4 times the global average carbon footprint of 4 tons per person.

What is a carbon footprint?

Every business, activity and individual has a carbon footprint.  The definition of carbon footprint is the measure of the amount of greenhouse gas produced by a person, business or activity. 


Everyone, and every animal, contributes an amount of greenhouse gas to our world. In addition, any activity or device that uses electricity has a carbon footprint. Rotting vegetation also has a carbon footprint.

Carbon emissions footprint
Carbon emissions footprint
Carbon emissions from electric power plant
Carbon emissions from electric power plant

What is Biofuel?

Biofuel is ethanol or plant oil.  Ethanol (biofuel) is alcohol produced from the fermentation of plants or other organic matter.  Alcohol can be produced by a number of processes.  Ethanol is a specific type of alcohol produced from plants.

In addition, biodiesel is also a biofuel. Biodiesel is plant based oil produced by pressing rapeseed, or other plants with high oil content. The term biodiesel is used to indicate that the diesel fuel has been extracted from plants rather than crude oil.

Biofuels offset carbon emissions

Increasing the use of biofuel is a straightforward way to reduce carbon emissions.  Biofuels are made from plants which absorb CO2 from air.  


When biofuel is burned, they return the CO2 originally absorbed by growing the biofuel crop.  Using biofuel in a vehicle simply recycles CO2 so no carbon is added to the air. 


A vehicle running on biofuel creates a true ZEV as it has a carbon neutral footprint.


Biofuel is the best option to reduce global warming. Increased use of biofuel reduces our use of fossil fuel.  Using biofuel, therefore, reduces carbon emissions which slows the rate of climate change.

What is a ZEV or Zero Emissions Vehicle?

The definition of a ZEV is a vehicle that produces no greenhouse gas or pollutants at the tailpipe.  A ZEV is a term used to market electric vehicles (EVs). 

If we ignore the Ozone (O3) emissions from electric motors, then EV’s are the only  commercially viable engine that currently has zero emissions at the tailpipe. 

The definition of a ZEV helps to sell electric vehicles as the term shifts focus from total carbon emissions to tailpipe emissions. A vehicle running on electricity is far from being ‘green’.

Tesla power station
Tesla power station
Nissan ZEV
Nissan ZEV

There are no carbon emissions from electric vehicles themselves although they are not carbon neutral.  EV’s have a large carbon footprint. .  

Driving an electric vehicle Electric simply shifts emissions from the vehicle itself to the power plant that charges it. For most people, however, out of sight is out of mind – If you can’t see the pollution, it isn’t there.

Although  EVs do not emit greenhouse gas directly, their batteries must be charged. As most electricity is produced by burning large amounts of fossil fuel, electric vehicles are not carbon neutral.

60% of electricity in the US is generated from fossil fuel.  This means that anything that uses electricity adds carbon dioxide to the air.

Big business are happy that you believe that electric buses, cars, trains, and bicycles, are zero emission.  How many cars do you think Tesla would have sold if they showed the electric cable connecting back to the smokestacks of the coal burning power plant that charged it? 

In addition, research has shown that manufacturing electric cars produces much more greenhouse gas than the equivalent petrol engine car.  A recent study of the Polestar 2 electric car showed that 24 tons of CO2 were created in manufacture compared to 14 tons for a similar petrol car. 

An average electric car created 60% more carbon emissions to manufacture than the equivalent internal combustion 4 stroke. 

Further to this, an average electric car battery emits 17.5 tons of carbon dioxide in production (more for larger electric cars). EV batteries have an expected life of 7 years.

Before going  too far off track with the mass of greenhouse gas produced in the manufacture of batteries, solar cells and other “green” products, I thought I’d link to an electric ZEV article which provides more detail of true zero emissions vehicles.

Over their expected life, electric vehicles do, at least, add less carbon than a regular internal combustion engine running on fossil fuel. 


Research on carbon emissions estimates that electric cars in Europe produce 30% less carbon emissions than the equivalent internal combustion car over its expected life (Electric car life ends with the expected 7 year battery life).  


In the US, electric vehicles would produce around 25% less carbon as US electricity production uses a higher percentage of fossil fuel.


The main benefit of electric vehicles is that they improve air quality in city centers. As electric vehicles displace pollution from the city to the power station they help keep cleaner air in our city centers.

Definition aside, the average person believes that a true ZEV is one that does not add greenhouse gas into the air.  

Currently, the only viable ZEVs that meet this expectation run on biofuel.  

An efficient 2 stroke combustion engine, running on biofuel, is the perfect zero carbon emissions vehicle.

The ZEV and 2 stroke engines

2 stroke engines can provide the perfect, low cost, ZEV.

2 stroke engines have been targeted by legislation as low cost engines are heavy polluters. As low cost 2 stroke motors need a mix of oil and petrol to lubricate the engine, blue haze can be seen from the exhaust of brushcutters, lawnmowers and chainsaws.

In addition, low cost 2 stroke motors provided the main form of transport for many emerging countries.  Many large cities have air quality problems and the smoke from a multitude of  low cost 2 stroke engines was an obvious contributor.

Ultra low emission 2 stroke trail bike
Ultra low emission 2 stroke trail bike
Ultra low emission 2 stroke engine
Ultra low emission 2 stroke engine

The abolition of low cost 2 stroke motors was an easy focal point for reduction in city smog. The smoke from cheap 2 stroke engines provided an obvious and visible target for legislation.

The problem is that legislation was written to ban 2 stroke engines rather than to address climate change. Legislation confuses pollution with greenhouse gas.

Even a low cost 2 stroke produces lower carbon emissions than a comparable 4 stroke or electric motor. 

In addition, 2 stroke motors can  run on biofuel which would create a true, zero emissions engine.

Two stroke engines can be easily re-engineered to run on ethanol biofuel which would create a true ZEV with carbon neutral emissions.  Carbon dioxide produced at the tailpipe is simply returning the CO2 absorbed by producing the biofuel.

Carbon footprint of 2 stroke engines

The carbon footprint of modern 2 stroke engines is lower than both 4 stroke engines and electric vehicles. Many scientific studies and real life data show that, not only are 2 stroke engines more efficient than 4 stroke motors but they also have a smaller carbon footprint.


Not only are greenhouse gasses lower when running on fossil fuel, but the use of biofuel can reduce carbon emissions from 2 stroke engines to zero. 


Electric motors are heavily marketed as zero emission vehicles, however, their carbon footprint is far greater than their 2 stroke counterparts.


As it is difficult (if not impossible) to change perception, the following section explains why the carbon footprint is lower in 2 stroke motors. We provide links to scientific papers and real time user data to allow you to verify the facts.

There are science studies that compare 2 stroke and 4 stroke emissions. Most compare basic, low cost 2 stroke engines against modern high efficiency 4 stroke engines with overhead camshafts, fuel injection, variable valve timing, catalytic converters and a raft of other emission reducing technology.  


Remember that 2 stroke engines have been systematically banned from most countries and motorsports over the past 25 years.  As their market has shrunk, comparatively little technical development has taken place on 2 stroke engines over this time.

These Findings would be reversed if air quality comparisons were made between using modern 2 stroke, port injected, engines against basic 4-stroke engines. Manufacturers were not given the opportunity to address emissions legislation before they were banned.

1. Lower fuel consumption

The primary goal of government legislation should be to reduce carbon emissions. 1 gallon of gasoline creates 20 pounds of CO2. A vehicle returning 10 MPG will, therefore, produce 4 times CO2 than a vehicle returning 40MPG.

Unfortunately, legislation regulates the % of pollutants within the burned gasoline but does not limit gasoline consumption. If bureaucrats are trying to lower carbon emissions, the primary goal should be to reduce the consumption of fossil fuel. 

Passenger numbers should also be a factor., A bus carrying 40 passengers is relatively beneficial to a car carrying 4. Legislating the size of the engine is difficult as trucks, buses, trains and ships require large engines.

Legislation should, logically, favor fuel efficient vehicles such as motorized bicycles, motorcycles and smaller cars rather than preventing relatively insignificant greenhouse gasses.

Scientific studies, and real life data, show that modern 2 stroke engines are more fuel efficient than 4 strokes. 

2 stroke vs 4 stroke engine
Fuel consumption of 2 stroke vs 4 stroke - Real world data

 It is difficult to find data on modern 2 stroke vehicles as legislation has banned them from most countries. We did, however, find 2 stroke motorcycle engines that allowed real life comparison.

We pulled fuel consumption data from two similar motorcycles chosen at random.  The bikes were both single cylinder, 250cc trail bikes from the same manufacturer.  The only major difference was the engines – A 2 stroke vs 4 stroke.

We pulled user statistical data for a 2015 Yamaha YZ250 2 stroke and a 2020, Yamaha WR250F 4 stroke. 

(We expect that the 2021 model would have been more economical but information on more recent models is hard to find). 

Fuel consumption figures collected from users shows:

  • The 2 stroke obtained a combined average fuel consumption of 89 MPG and
  • had a more powerful 48.8HP engine.  


  • The 4 stroke obtained a combined average fuel consumption of 61 MPG and
  • had a less powerful 30HP engine.

(MPG figures are in UK gallons).


Statistically then, the 2 stroke engine is 46% more fuel efficient while at the same time providing 62% more power.  In addition the 2 stroke engine is lighter, more compact and less complex.


If we use this data to compare power against fuel consumption, the 2 stroke motor is 237% more efficient.


This is simply, real time, comparison that we selected at random.  We encourage readers to undertake further comparisons.

2. Higher power to weight ratio - Smaller carbon footprint

The carbon footprint of an engine measures the total amount of greenhouse gas that an engine will produce over its life. This includes all carbon emissions produced during manufacture and while running.


2 stroke engines are smaller and less complex than 4 stroke motors and can be half the weight of a 4 stroke of the same power.  They, therefore, produce substantially less carbon in manufacture.

3. Use of lower grade fuels

The use of low grade fuel oil, combined with engine weight/size reduction and fuel economy, has been useful for shipping for many years. 


Low grade fuel is used primarily to reduce fuel costs, however, the ability to run on lower grade fuel provides flexibility when considering biofuel production techniques.

4. Use of biofuels

Legislators fail to promote the simple solution of using eco friendly biofuels. Diesel cars can run on 100% rapeseed oil as this is promoted to be eco-friendly. 


DIluting pure alcohol with less than 1% rapeseed oil is all that would be required to run a 2 stroke engine.

2 stroke advancements

5 Potential for future efficiencies

There has been very little development in 2 stroke engines over the past 20 years.  Where massive investment has taken place to improve the efficiency of 4 stroke engines, 2 stroke motors have been left on the shelf.

Where technical development of 4 stroke engines is reaching a plateau, 2 stroke engines have a huge scope for further improvement. 

6. Lower carbon emissions and pollutants

Modern 2 stroke engines require far less oil than earlier models and the CITS 2 stroke requires no oil/fuel mix at all. 

Modern 2 strokes can exceed Euro4 Ultra Low Emission legislation which was written to limit pollutants from gasoline vehicles.

Where 2 strokes of the 1990’s required mixtures of 30:1, modern 2 strokes currently in production can run on an oil to gasoline ratio of 150:1 

There are many other scientific studies that show that 2 stroke engines emit fewer pollutants than 4 stroke engines. The study linked here compares the improvements in power, efficiency, and reduced pollutants of large 2 stroke engines compared with 4 stroke counterparts.

This link provides details of an Australian designed crankcase independent 2 stroke (CITS) engine which is lighter and more powerful and emits fewer pollutants  than 4 stroke engines. The prototype was built several years ago but has, until recently, failed to attract any interest from investors.

Modern 2 stroke engines use fuel injection and engine management systems.  Just as in a modern 4 stroke, the Engine Management System (EMS) detects emissions at the tailpipe. The EMS can regulate gas/oil mixture entering the combustion chamber to ensure that there are no unburned fuel.

The KTM 300 cc 2 stroke motorcycle complies with strict Euro 4 standards.  To put this in perspective, this 2 stroke motorcycle could be driven, alongside electric cars, in London’s Ultra Low Emissions Zone without charge.

Change to Ethanol for the perfect ZEV

By simply changing the fuel / oil to biofuel, the 2-strokes become the perfect ZEV. By burning alcohol instead of fossil fuels, most pollutants are removed.  


An engine running on alcohol changes the 2-stroke engine into the environmental wonder that the world has been seeking.


Modern 2 stroke engines are more efficient, have lower carbon footprint. lower carbon emissions and emit fewer pollutants than either 4 stroke engines or electric vehicles. 


Modern 2 stroke engines can run alongside electric vehicles that comply with emission requirements in London’s Ultra Low Emission Zone. 


4 stroke technology advancement has plateaued. Further fuel efficiencies will be difficult to obtain. The comparative lack of investment in 2 stroke engines leaves scope for further development. 


In addition, the Euro zone and the UK have announced that they will move to full electric vehicles over the next few years by imposing a complete ban on all internal combustion engine vehicles.  Over their 7 year life expectancy, electric cars can reduce carbon emissions by up to 30% compared to a car with an equivalent 4 stroke engine. A comparative 2 stroke vehicle running on biofuel would reduce carbon emissions by 90%.


Legislation confuses pollution with emission.  Legislation intended to slow global warming  focuses on the percentage of minor greenhouse gasses rather than the volume of carbon emissions.


Until the world completely replaces fossil fueled power plants with renewable energy alternatives, biofuel is our best option to reduce carbon emissions.

Motorized Bikes
Carbon emissions and the 2-stroke ZEV (zero emission vehicle)
Power Bicycles
Carbon emissions and the 2-stroke ZEV (zero emission vehicle)
Information about motorized bikes
The 2 stroke engine is the worlds best option to reduce carbon emissions and can be used to engineer a true ZEV (zero emissions vehicle). As 2 stroke engines are mistakenly perceived to be polluting, highly inefficient gas guzzlers, we provide a mass statistics, real life data and scientific research to back up our statement.
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