China, the world’s biggest producer of commodities including coal and gold, is moving to reform its resources tax system, underlining Beijing’s determination to push ahead with environmental reforms under its five-year plan.

Broadly speaking, the tax reforms will shift from volume-based taxes, set years ago and generally very low, to value-based taxes that will fluctuate alongside commodity prices. The new system was implemented for oil and gas late last year, and is expected to be extended to coal and other commodities.

In pushing through environmental reforms such as the resources tax, Beijing faces a delicate balancing act as policymakers try to protect the balance sheets of powerful state-owned energy companies, including large industrial groups such as CNPC, Shenhua, State Grid and Sinopec.

China is the biggest energy user in the world, and Beijing’s energy policies often ripple far beyond its borders, affecting pricing and demand for commodities such as coal, oil and liquefied natural gas.

On November 1 the resources tax for oil and gas moved from volume-based (between Rmb8 ($1.30) and Rmb30 a tonne for crude oil) to a value-based tax set at 5 per cent of the value of the oil and gas produced. At today’s prices, that equates to a tax increase of 10-20 times for crude oil.

But the net impact on China’s oil companies will be minimal because the government offset this increase with separate changes to the windfall profits tax – backdated to November 1 to match the day the resources tax was changed – that will largely balance that out.

Shares of PetroChina, the listed subsidiary of CNPC, and Sinopec rallied on the news, underscoring investors’ views that it was a small victory for China’s enormous oil companies.

Beijing in recent years has been trying to make the country more energy-efficient and less fossil fuel-dependent. Policies, including electricity price reform, resources tax reform and the introduction of a carbon tax, have been on the political agenda but have often stalled because of concerns about their impact on the economy. At the heart of the changes is the premise that if fossil fuels became costlier it would encourage consumers to move away from them and to use less energy in general, two things the government wants to encourage.

This balancing act will face a greater test when the government extends the resources tax reform to its coal sector, the world’s largest in terms of tonnes mined each year. Officials have for the past three years talked about moving from a volume-based to value-based tax system there too, but have held off in the face of opposition from companies and concerns about potential macroeconomic fallout from higher coal prices. It is expected to be pushed through before 2015.

China relies on coal for 80 per cent of its energy, and rocketing prices for thermal coal have made Beijing reluctant to push through tax changes that could raise coal costs. Unlike production of crude oil, which is encouraged to avoid imports, Beijing is trying to cap coal production, and the potential tax changes on coal could have a bigger impact than for oil and gas.

Details about the coal tax have been scarce, but analysts believe Beijing will follow the oil and gas model and introduce a value-based tax of about 5 per cent on coking and thermal coal. At current thermal coal prices, that would equate to a tax rise of about Rmb20 a tonne, or more than Rmb60bn of extra taxes per year.

Analysts say such an increase is likely to be paired with a move to streamline the local taxes on coal miners to ameliorate the impact on coal miners’ balance sheets.

China’s policymakers also face hurdles pushing through a carbon tax. Although the initial price mooted by state media – Rmb10 a tonne of carbon – is low by global standards, a tax would still have a big impact on the power and heavy industry sectors.