The article is saying that we can't expand biogas to replace all our current gas usage. Which is fine, as electricity meets most of those needs better anyway (e.g. heat pumps for home or industrial heating/cooling, renewables for the majority of electricity).

But the article also states that non-food based manure biogas could be expanded to 3x current with no impact on food (well, except to make German meat and dairy more GHG friendly). Food waste is another source that doesn't compete for land. Coal mines and landfills leak methane. New satelitte tech can pinpoint small sources and fine people that don't capture it, providing both a stick and a carrot.

So, the small amount of unavoidable gas usage, can be met by capturing stuff that would otherwise be released as methane. We already have gas storage and gas turbines. We can mix in green hydrogen too if need be.

50% is the capacity we need, not the amount of energy that needs to be supplied.

Here's a Wartsila projection for Germany suggesting 8% "flexible gas" is what's required, with 59% of peak capacity. That is, a very small amount of the year, it's used a lot. Luckily we already have large amounts of gas storage built. (Also, we've done a complete loop on this thread: "Gas generation capacity is different from GHG and other pollutants caused by actually burning fossil gas. Don't be fooled by people implying they are the same.")

https://www.wartsila.com/energy/towards-100-renewable-energy...