ITV Cymru Wales has had a first look inside Cardiff's modern incinerator since it started operating earlier this year.
The plant will burn up to 350 thousand tonnes of household waste a year and is now running 24 hours a day, 7 days a week.
The site says the burning process is safe and effective but environmentalists argue it's the wrong answer to our waste problems and the health effects are still unknown.
Watch Alexandra Lodge's report:
Councillor Louise Hughes, of LLanegrin in Gwynedd says the move to a three week black bag collection was a big and expensive mistake.
She said, “It’s ridiculous. They did a questionnaire and had almost 2,000 responses and most people said ‘no way’. I can’t believe they’re going to go ahead, it will be a complete, unmitigated disaster.
“What it will mean especially for coastal towns is seagulls will be ripping open bin-bags. What is the point of consultation and then saying ‘we’re going to do it anyway’?”
The new collection regime will come into force in October and will take 18 months to introduce. Gwynedd County Council says it will save £350,000.
Gwynedd Council has become the first in Wales to introduce black bag collection every three weeks.
Councillors say it'll save £350,000 and recycling and food waste bins will still be collected weekly.
Diana Hulme on Facebook says says, "Do we get a reduction in our council tax to reflect the reduction in the number of collections???? Let me guess...no."
Stephen Giffard on Twitter add, " That's good news for rats I suppose."
Ben Jones on Facebook says, "Living with my partner and a 2 year-old baby and the bin is packed to the top after 2 weeks as it is. We recycle its not as if we just throw everything in one bin!"
Mared on Twitter says, "Disgusting health hazard. Are GCC going to slash the council tax to reflect the loss of services? No, I thought not!"
Dustbins in Gwynedd will be emptied every three weeks instead of fortnightly following a vote by councillors.
The unanimous decision was taken by cabinet members claiming it was a sensible step repeated in other parts of the country.
The new timetable will come into force in October and will take 18 months to introduce throughout the county - it's claimed it will save £350,000.
The council heard that public surveys have shown that half of people anticipate problems with such things as nappy disposing. There were also concerns over rats, smells and bins becoming too heavy.
However there will be no changes to weekly household recycling, and food waste services, and a fortnightly collection of garden waste says the council.
Currently only half of Gwynedd residents use recycling bins.
“We must take steps to persuade those residents who continue to throw waste that can be recycled into their residential waste bins to start using the weekly recycling and food waste services,” says Councillor Gareth Roberts.