Reuters: Japan’s power firms paid a combined 100.1 billion yen, or $1 billion, for carbon credits in the year that ended on March 31, their annual earnings reports showed, giving investors a rare glimpse into how much utilities are spending to offset their own carbon emissions. The sector is one of the biggest buyers of carbon credits from abroad and is expected to buy more as it struggles to meet its voluntarily set targets, which were based on a model in which its carbon-free nuclear plants …