Tallinn seems to be leaning towards the use of electric buses, with bio-gas-fueled buses as an intermediate interim, while Tartu, Tartu County and also Pärnu already use bio-gas on all or most of their public transport.

Other options include hydrogen; considerations include the feasibility of different fuels, as well as lobbying from business interest groups.

Tallinn deputy mayor Andrei Novikov (Center) confirmed the future of public transport in the capital still lies with zero-emissions transport.

Novikov told AK that: "Today we are focusing on gas buses, but if we look at our strategy, we will completely abandon diesel buses by 2025 and we have electric transport planned for 2035, so the current is somewhat intermediate".

"After an interim phase, we will definitely see only electric transport on our streets in the future," Novikov went on.

Lennart Viikmaa, Tallinn Transport (TLT) board member noted that the transition phase is indeed underway, with bio-gas-fueled buses quite numerous now, instead of the old diesel models.

He said: "200 gas buses already serve Tallinn city lines. An agreement has been signed for the purchase of additional bio-gas buses, one hundred of these, plus an option for 50 buses more."

While deputy mayor Novikov thinks that these are good as an interim measure to 2035, TLT sees the investment as one for the longer-term.

Meanwhile in Estonia's second city, Tartu, all buses run on bio-gas via a procurement set to last the rest of this decade. Tartu deputy mayor Raimond Tamme (Reform) said that while it cannot be predicted yet what will fuel the city's buses after that, no carbon-neutral fuel source is off the table at present.

Academic Enn Lust, who heads up the University of Tartu's physical chemistry faculty, told AK that one option may be hydrogen, which can be produced via solar energy.

He said: "In order to produce the cheap fuel called hydrogen, we need to set up a large solar park near Tartu, which [real estate and energy firm] Estiko plans to build at the old Raadi airfield."

The  European Commission's far-reaching climate package unveiled Wednesday includes restrictions on transport fuels, with fossil fuels required to be phased out altogether. While it emits CO2, bio-gas is not a fossil fuels.

It is not yet produced in sufficient quantities to be the sole or main fuel source as yet, however.

Kristjan Stroom, CEO of Eesti Biogas OÜ, told AK that: "As of today, I think that public transport could use three times more bio-methane than is available on the market. One hundred percent of the bio-methane we produce is used to run both Tartu city and county buses and, for example, Pärnu public transport. In Tallinn, I would venture to say this percentage is at present relatively low."

Enn Lust says the feasibility of the introduction of hydrogen largely depends on how quickly the necessary changes can be implemented – required solar parks could take a couple of years to install.

With regard to bio-gas, he said that: "Everything about green gas depends on whether we have it, on the basis of what technology is used to produce it, since the production of green gas itself generates CO2."

The fuel also had political and business interests tied to it, he said.

"It was a populist solution pushed through by Estonian politicians with the interests of a certain business group in mind, using a long-term perspective," he went on.

Some commentators doubt that hydrogen buses will be in use in Tartu by 2030 either.

Madis Vasser, board member of the Estonian Greens, said that: "This presupposes that large parks exist, but we do not have many today. Second, it presupposes that there would be sufficient electricity left over [to generate hydrogen]".

"The question is what energy system are we committed to. Biomethane; it seems that this is being made anyway, it is locally available and we already have buses that run on it," he went on.

Raimond Tamme, Tartu's deputy mayor, said one green fuel cannot be preferred to another at this point in time.

He said: "As of today, bio-gas buses are still so much cheaper than others. If hydrogen buses are at a reasonable price at the moment, then the city of Tartu is definitely interested. The cleaner the fuel solution, the better."

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