INTRODUCTION
Everything we do, from the food we eat, products we buy to the way we travel, releases greenhouse gases into the atmosphere, and so has an impact on the planet's climate. But some activities have a far greater impact than others.

Around 2.4% of global CO2 emissions come from aviation. Together with other gases and the water vapour trails produced by aircraft, the industry is responsible for around 5% of global warming.

At first glance, that might not seem like very big contribution. Except, only a very small percentage of the world flies frequently. Even in richer countries like the UK and the US, around half of people fly in any given year, and just 12-15% are frequent fliers. Greenhouse gas emissions from the aviation sector are a substantial contributor to global warming. If the aviation industry were a country, it would place sixth in emissions, between Japan and Germany. Left unchecked global aviation will generate an estimated 43 metric gigatons of carbon dioxide emissions through 2050, constituting almost 5% of the global emissions allowable to keep global warming below 1.5 degrees Celsius.

The effect is so large today that it exceeds the total warming influence of all of the CO2 emitted by aircraft since the beginning of powered flight. The atmospheric graphic presents a range of the warming from contrails and contrail-induced cirrus clouds, identified as cirrostratus, since the atmospheric conditions that produce and sustain contrails vary over time and space.

Source: atmosfair.com Red color -warming impact ,Blue color -cooling impact Red colour -Warming impact ie, As greenhouse gases trap more energy from the sun, the oceans are absorbing more heat, resulting in an increase in sea surface temperatures and rising sea level.

Blue colour - Cooling impact ie, Ocean currents act as conveyer belts of warm and cold water, sending heat toward the polar regions and helping tropical areas cool off, thus influencing both weather and climate.

GREEN HOUSE GASES EMISSIONS
- Green house gases emissions from all commercial operations in 2018 totalled 918 million metric tons-2.4% of global GHGs missions from fossil fuel use. Using aviation industry values, there has been a 32% increase in emissions over the past five years.(Source-www.eesi.org)
- Modern jets cruise in the upper troposphere, which extends from ground level up to about 6.2 miles, and lower stratosphere, beginning at around 33,000 feet. The tropopause is the boundary layer between the troposphere and the stratosphere.
- Along with carbon dioxide(CO2), jet engines emit water vapour (H2O), nitrogen oxides including nitric oxide (NO) and nitrogen oxide (NO2) (together termed NOx), carbon monoxide (CO), N2O, partially combusted hydrocarbons (volatile organic compounds or VOCs), particulates (soot), and other trace compounds.(Source-www.eesi.org)
- The impact of CO2 emissions on climate is the same irrespective of its source. It makes no difference whether it comes from a power plant in Nebraska or a Lear jet at 40,000 feet over Europe, the CO2 emitted mixes with the global atmosphere over many decades or even hundreds of years.
- For NOx , N2O and H2O emissions, climate impact is localized and amplified at high altitude. Nitrogen oxides chemically react with light to form ozone (O3). The higher intensity of light in the upper atmosphere produces more ozone from NOx emissions, and these emissions have more influence on climate than those same emissions at ground level.
- Water vapor is a potent and short-lived greenhouse gas, present mostly at lower altitudes. Introducing H2O into the normally dry air of the upper troposphere and lower stratosphere create the condensation trails we've all seen and possibly the formation of cirrus clouds. Since cirrus clouds don't typically form in the upper atmosphere, there remains uncertainty as to the impact on climate, though studies suggest that these high-altitude clouds have an insulating effect, trapping heat.

AIRPORT CARBON ACCREDITATION (ACA)
It is an Airport Carbon Management certification standard . The plan independently evaluates and recognizes the efforts made by airports in managing and reducing carbon emissions through four award levels. Airport Carbon accreditation is the only global airport carbon management certification program recognized by the organization. It independently assesses and recognizes airport management and carbon emission reduction efforts through 6 levels of certification: "Mapping", "Reduction", "Optimization", "Neutrality", "Transformation" and "Transition"(Source-aci.org).Through its 6 levels of certification, the airport carbon certification recognizes that the airport is at different stages of the comprehensive carbon management journey. The plan is applicable to airports of all sizes, from central airports and feeder airports with regular passenger traffic togeneral aviation and cargo airports.

What are the benefits of airport accreditation ?
- Recognize your efforts in managing and reducing carbon emissions.
- Reduce costs by effectively managing carbon emissions.
- Communicate your green certificate to external stakeholders.

How does it work?
Airports are at different points on the journey to becoming cleaner and more efficient. As the centre points of a complex web of aircraft movements, technical operations and surface access transport, airports can address their CO2 emissions in a variety of ways. These can include better insulation and energy efficiency, switching to green energy sources, investing in hybrid, electric or renewable gas-powered service vehicles, encouraging employees, passengers and visitors to use public transport, working with airlines and air traffic management to reduce runway taxiing times and implement green landing processes and much. From an exploratory initiative that began with 17 of the environmentally most advanced airports in Europe in the first year (2009-2010), it has become a global industry standard for airports all over the world, with 274 accredited airports worldwide as of June 2019. These airports are located in 71 countries across all continents and welcome close to 44% of global air passenger traffic almost every second passenger in the world is travelling through a Carbon Accredited airport today. They are small and large, commercial hubs and general aviation airports, situated in the biggest countries of the world and in the small island States. They are at different stages in the carbon management journey. Airport Carbon Accreditationprovides a general framework and beacons, but the exact path is charted by each airport individually, as is the pace of its progress.

6 levels of accreditation
The programme provides a unique common framework and tool for active carbon management at airports with measurable results. It covers the operational activities that contribute most to carbon emissions. It is site-specific and can be used at any airport as part of its daily environmental management activity and long term strategy as it helps to guide and support airports through a process of continual improvement and partnership with stakeholders.

Source : iitccu.com

CORSIA
CORSIA is a global offsetting scheme, whereby airlines and other aircraft operators will offset any growth in CO2 emissions above 2020 levels. This means that aviation's net CO2 emissions will be stabilised, while other emissions reduction measures.

Developed by the International Civil Aviation Organization (ICAO) and adopted in October 2016. Its goal is to have a carbon neutral growth from 2020. CORSIA uses Market-based environmental policy instruments to offset CO2 emissions: aircraft operators have to purchase carbon credits from the carbon market. Starting in 2021, the scheme is voluntary for all countries until 2027.

To secure a political agreement in ICAO and address the concerns of developing countries, the implementation of CORSIA has been divided into three phases - two initial, voluntary phases (2021-2023 and 2024 - 2026) and a mandatory phase that would take place from 2027.(Source-ICAO) Source: corsia.iittp.com During the initial phases, CORSIA will only apply to international flights between states that have volunteered to take part, meaning that international flights to and from states that have not volunteered will be exempt.In October 2016, the 191 nations of the ICAO established the scheme, requiring operators to purchase carbon offsets to cover their emissions above 2020 levels, starting from 2021. Forestry and carbon-reducing activities will be funded by 2% of the sector annual revenues, avoiding "double counting" of existing efforts.CORSIA is voluntary until 2027, but many countries including the US and China, promised to begin from the 2020 start. The WWF saw carbon credits as credible, but the scheme appears insufficient in the long run while review periods are included.

During the mandatory stage, which begins in 2027, CORSIA will cover all international flights (including those travelling to or from states that had not volunteered for the early phases)

STRATEGIES FOR AVIATION EMISSIONS MITIGATION
- Reducing air travel
Aviation's environmental impact would be mitigated by reducing air travel, route optimization, emission caps, short-distance restrictions, increased taxation, and decreased subsidies.

- Route optimization
An improved Air Traffic Management system, with more direct routes than suboptimal air corridors and optimized cruising altitudes, would allow airlines to reduce their emissions by up to 18%.

- Short-haul flight ban
A short-haul flight ban is a prohibition imposed by governments on airlines to establish and maintain a flight connection over a certain distance, or by organisations or companies on their employees for business travel using existing flight connections over a certain distance, in order to mitigate the environmental impact of aviation. In the 21st century, several governments, organisations and companies have imposed restrictions and even prohibitions on short-haul flights, stimulating or pressuring travellers to opt for more environmentally friendly means of transportation, especially trains

- Taxation and subsidies
Financial measures can discourage airline passengers and promote other transportation modes and motivates airlines to improve fuel efficiency. Aviation taxation include:
- Air passenger taxes, paid by passengers for environmental reasons, may be variable by distance and include domestic flights;
- Departure taxes, paid by passengers leaving the country, sometimes also applies outside aviation

Consumer behaviour can be influenced by cutting subsidies for unsustainable aviation and subsidising the development of sustainable alternatives.

Aviation taxation could reflect all its external costs and could be included in an emissions trading scheme. International aviation emissions escaped international regulation until the triennial conference in 2016 agreed on the offset scheme.Due to low or nonexistent taxes on aviation fuel, air travel has a competitive advantage over other transportation modes

- Alternative fuels
An aviation biofuel or bio-jet-fuel or bio-aviation fuel is a biofuel used to power aircraft and is said to be a sustainable aviation fuel (SAF). It considers it to be one of the key elements to reduce the carbon footprint within the environmental impact of aviation Aviation biofuel could help decarbonize medium- and long-haul air travel generating most emissions, and could extend the life of older aircraft types by lowering their carbon footprint.

Aviation biofuel can be produced from plant sources like Jatropha, algae, tallows, waste oils, palm oil, Babassu and Camelina (bio-SPK).Plants absorb carbon dioxide as they grow, meaning plant-based biofuels emit only the same amount of greenhouse gases as previously absorbed. Biofuel production, processing and transport however emit greenhouse gases, reducing the emissions savings.Biofuels with most emission savings are those derived from photosynthetic algae (98% savings, technology not yet mature) and from non-food crops and forest residues (91-95% savings).

Jatropha oil, a non-food oil used as a biofuel should lower CO? emissions by 50-80% compared to Jet-A1. Jatropha, used for biodiesel, can thrive on marginal land where most plants would produce low crop yields. A life cycle assessment by the Yale School of Forestry on jatropha, one source of potential biofuels, estimated that using it could reduce greenhouse gas emissions by up to 85% if former agro-pastoral land is used, or increase emissions by up to 60% if natural woodland is converted to use.

Palm oil cultivation is constrained by scarce land resources and its expansion to forestland cause deforestation and biodiversity loss, and direct and indirect emissions due to land-use change.Neste's renewable products includes a refining residue of food-grade palm oil, and the oily waste skimmed from the palm oil mill's wastewater. Neste's sustainable aviation fuel is used by Lufthansa.

NASA has determined that 50% aviation biofuel mixture can cut particulate emissions caused by air traffic by 50-70% Biofuels do not contain sulphur compounds and thus do not emit sulphur dioxide.

Sustainable biofuels do not compete with food crops, prime agricultural land, natural forest or fresh water. They are an alternative to electro fuels Sustainable aviation fuel is certified as being sustainable by a third-party organisation.

Aviation biofuels: which airlines are doing what, with whom?
- United Airlines, Boeing, Honeywell's UOP, the Chicago Department of Aviation and the Clean Energy Trust announced the formation of the Midwest Aviation Sustainable Biofuels Initiative (MASBI), designed to advance aviation biofuel development in a 12-state region holding significant promise for biomass feedstock, technology development, job creation and sustainable commercialization.

- Alaska Airlines said its decision to use 20% biofuel during its 75-flight biofuel commercialization program was limited to 20% because of lack of supply. With the fuel produced in Louisiana from used cooking oil, refined in Texas and sourced by a broker the Netherlands, the supply chain was very difficult. Beyond that, it cost $17 per gallon compared to $3.14 per gallon for A1 jet fuel.

- Porter Airlines successfully conducted the first biofuel-powered revenue flight in Canada. In the successful conclusion to a test program that was launched in 2010, the airline flew one of its Bombardier Q400 turboprops from its base at Billy Bishop Toronto City Airport to Ottawa using a 50/50 blend of biofuel and Jet A1 fuel in one of its engines.

- Netherlands-based SkyNRG supplied LAN Chile and Air BP Copec for its first commercial flight with second generation jet fuel. The flight, which operated between the Chilean cities of Santiago and Concepcion, was conducted on an Airbus from the A320 family with CFM56-5B motors. The fuel came from used cooking oil.

- Lufthansa have signed a Memorandum of Understanding to jointly evaluate the potential for algae oil from Algae.Tec's bio-reactors to be developed into a sustainable source of aviation biofuels

- Air France completed its first biofuel-powered scheduled passenger flight, running on a 50/50 combination of traditional jet fuel and jet fuel produced from used cooking oil. Together with "optimised" air traffic management (ATM), the flight saved roughly 50% of its CO2 emissions, bringing the per passenger emissions rate down to 54g per kilometer.

SUSTAINABLE AVIATION FUTURE
Future developments regarding sustainability in the aviation industry are going to be reliant upon three groups having the foresight and determination to drive change.

Firstly, the existing aviation industry players who have taken on the task of revolutionizing existing practices. Major OEMs have made bold statements about their commitments toward a sustainable future.

The second group comprises the start-up manufacturers, infrastructure developers and software companies producing entirely new operating platforms. This group's role is to challenge the status quo and includes the development of Advanced Air Mobility (AAM), networks of electric charging stations, pilotless aircraft and clean fuel, amongst other emerging technologies.

The last group comprises the policymakers, regulators and governments. Their challenge is immense and not to be overlooked. Simply put, it is to set bold targets and create the framework for innovation and certification that allows those targets to be met.

The whole aviation supply chain needs to be jointly accountable for achieving industry sustainability. OEMs investing in green fuels need to believe that the infrastructure, including at airports, will be able to support those initiatives. Additionally, subcontractors, service providers and even insurance providers need to be challenged as to how they are transforming their own businesses to achieve greater sustainability.

While beneficial, carbon offsets are broadly seen only as short-term relief from a much larger predicament.

ICAO SAFETY ON AVIATION
Safety is a core value-offering of rapid and dependable air services, and international cooperation on aviation safety by governments and industry groups, through ICAO, has helped to make commercial aircraft the safest way to travel.

The 193 countries who cooperate through ICAO are currently working toward their agreed global safety target of zero fatalities by 2030, in tandem with the strengthening of their regulatory capacities, while pursuing a range of programmes and targets relevant to current core areas of global aviation safety planning, oversight, and risk mitigation.

ICAO Audit
ICAO audits the aviation safety and aviation security oversight capacities of its 193 Member States. In the Safety domain these are carried out under our Universal Safety Oversight Audit Programme (USOAP), while in the security domain we operate a similar Universal Security Audit Programme (USAP).

It is important to recognize that these audits do not cover airlines, airports or other industry operators. Rather they are restricted to only the legislation, resources and other capacities which State governments establish in order to effectively implement ICAO's Standards and Recommended Practices (SARPs) in each area.

Aggregated USOAP results may be reviewed interactively by the public on ICAO's website. Security audit results are confidential and are not made public. They are, however, shared with other Member States through suitably confidential mechanisms.

They are also working to enable the safety standardization needed to integrate today's exciting innovations in aircraft propulsion, design, autonomous control, and personal mobility, while still maintaining or improving overall network performance.

Conclusion
While the challenge is significant, the building blocks are in place to enable the next phase of aerospace development to achieve much greater levels of sustainability in the aviation industry while lessening its carbon footprint. Increasing public concern about climate change, coupled with governmental support of green initiatives, should help innovation in this area to flourish.

The mission has begun on many fronts! Even though some corporate and governmental target dates for a cleaner environment seem far away, positive change will become more evident every year. As it works with many entities at the leading edge of this transformation, Global Aerospace can attest to the advancements being made in numerous areas and is fully supportive of development initiatives throughout the industry.

The aerospace industry has always been at the cutting edge of technology. It now has an opportunity to create solutions that will have an impact far beyond air travel. Transformation can be realized that will ensure the next era of development can continue aviation's legacy of connecting the global community, but with a lower impact on the planet upon which it depends.

We at Carbon Minus India (CMI), an Initiative of Indian Institute of Sustainable development (IISD); are working in Aviation Carbon Management for last more than 7+ Years. We have the expertise of estimating Aviation Carbon Emission and Recommending for achieving Net Zero Carbon Footprint in aviation sector, as well. Our Team-IISD Members, Aviation Carbon Management Division (ACMD) has completed a number of Consultancy and Research assignments in this challenging professional field of domain with many National and International Clients .Carbon Minus India (CMI) has begged a prestigious Consultancy Assignment recently, competing in an International bidding process from Airport Authority of India (AAI) for Organizing the Verification of Airport Carbon Accreditation (ACA) by Airports Council International (ACI), Brussels, Belgium of first 4 International AAI Airports of India, such as Varanasi, Bhubaneswar, Kolkata and Thiruvananthapuram. The ACA Verification Process of these Airports for Level-1 and Level-2; are already completed and subsequently Certified All by 7th January, 2020. In addition, We have 3 ICAO trained, CORSIA Verifiers available with us. We have imparted a Number of Capacity Building Training and Safety Programs in 5 Countries Of South East Asia and Middle East by now on Aviation Safety, Air Port Carbon Accreditation (ACA) Audits and Certifications' and Regulation and Implementation of CORSIA for monitoring of International Aviation Emissions and How to Prepare Necessary ICAO based CORSIA Inventorization. In addition, We have Organized many Workshops, Roundtables and Webinars and Prepared Documentations on related Matters.

BIBLIOGRAPHY
1. IEA. Global Energy and CO2 Status
2. https://www.easa.europa.eu/eaer/topics/market-based-measures/corsia
3. https://www.icao.int/safety/Pages/default.aspx
4. https://www.airportcarbonaccreditation.org/
5. https://www.icao.int/environmental-protection/pages/a39_corsia_faq2.aspxIATA. Industry Statistics: Fact Sheet
6. IEA. Global Energy Review 2020
7. Low-Carbon Fuels for the Maritime, Aviation and Haulage Sectors. Adv. Appl. Energy 2021, 1, 100008.
8. Kaufmann et al. ,Mitigating the climate impact from aviation.
9. ICAO. On Board a Sustainable Future
10. ICAO. United States Aviation Greenhouse Gas Emissions Reduction Plan.
11. Beyersdorf,A.J. Biofuel blending reduces particle emissions from aircraft engines at cruise conditions. Nature 2017
12. McElroy, P. Boeing and Sustainable Aviation Biofuel Development
13. Hawthorne, P. Land clearing and the biofuel carbon debt. Science 2008, 319, 1235-12


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We have a professional team engaged in Aviation Carbon Management for last more than 5 Years. We have the expertise of estimating Aviation Carbon Emission and recommending for achieving Zero Carbon Footprint in aviation sector. Our Aviation Carbon Management Group (ACMG) has completed a number of Consultancy and Research assignments in this challenging professional field with many National and International Clients. We closely work with the Policy Framework and Guidelines Prescribed by International Civil Aviation Organization (ICAO), Montreal, Canada and International Emission Trading Association (IETA), Geneva, Switzerland. We have trained professionals to conduct Green House Gas (GHG) Emission Reduction Audit and Organizing Carbon Footprint Assessment, Verification and finally recommending for Certification.

Indian Institute of Sustainable Development (IISD)’s sister concern Carbon Minus India (CMI) has begged a prestigious consultancy assignment recently, competing in and International bidding process from Airport Authority of India (AAI) for Organizing the Verification of Airport Carbon Accreditation (ACA) by Airports Council International (ACI), Brussels, Belgium of first 4 International AAI Airports of India, such as Varanasi, Bhubaneswar, Kolkata and Thiruvananthapuram. The ACA Verification Process of these Airports for Level 1, is already completed and subsequently Certified. However, at present the Green House Gas (GHG) Emission Audit for ACA Level 2 is going on. We have 2 ACA Verifier Professionals are available with us. 2 Photographs from Varanasi International Airport, One in Day and Other in the Night have been displayed here.