The recycling business has always had ups and downs, good times and bad, with some better and some worse than others.

End markets can change, sometimes quickly, making products like glass bottles and many consumer plastics unwelcome at recycling centers. World events and political maneuverings can impact what happens to a cereal box.

The U.S.-China trade war has put new twists on recycling everything from beer cans to scrap metals and plastics from manufacturing plants to used office paper. While there has been a great deal of attention this week to what the U.S. government has called progress in its talks with China on the trade war, there are few specifics. Whether any action will affect the recycling situation is not known at this time.

China provided a worldwide jolt when it announced in July 2017 that in January this year it would ban 24 types of waste from the United States. It imposed tariffs on other kinds of waste. Exporters and others in the waste industry expect more tariffs soon because they see no negotiated end to the trade war.

Then this year, China imposed a strict, enforced limit on “contaminated” recyclables shipped from the United States to China for recycling to provide raw materials for the many products made there.

Examples of contamination include unlike materials mixed together, dirty materials that have to be cleaned before recycling and greasy pizza boxes. These things can spoil an entire load and cause it to be sent to a landfill, according to industry publications and websites.

“Though the regulation is primarily designed to address major environmental and health issues in China, it will also be a genuine global disrupter,” the South China Morning Post, an English-language newspaper published in Hong Kong, reported in July this year. “It has the potential to propel many waste-exporting countries who for far too long have taken an ‘out of sight, out of mind’ attitude to waste disposal — to adopt far more progressive disposal and recycling systems.

“Since the 1980s, China has become the world’s largest importer of waste, or ‘foreign trash,’ as it is commonly called in Chinese,” the newspaper reported. “By 2012, up to 56 per cent of global-exported plastic waste ended up in China.”

China started a 10-month “Green Fence” program in 2013 in which it began changes that it said were good for the environment. Among them was limiting the amount of contamination.

This year, as part of the sequel to “Green Fence,” China launched its “National Sword” policy, which included dropping the contamination level to .5 percent — one-half of 1 percent. Recycling exporters and industry groups said there was no way that the new level could be met.

Waste industry officials around the country say a major reason there is so much contamination is “wishful recycling” or “aspirational recycling” — when people with good intentions or ignorance put items that cannot be recycled into their recycle bins in the hope or the expectation that it will be recycled.

It costs money to pull those things out of the sorting process, often the last step after mechanical sorting has taken place.

Sometimes loads with a lot of these materials are sent to landfills without sorting out what could be recycled, according to industry experts.

A monetary result is that instead of the recycling center or hauler making money by selling the load, a landfill fee has to be paid.

The volume of recycling materials from the U.S. to China has fallen drastically, from 4,000 shipping containers a day to only hundreds.

Last year, $5.6 billion worth of scrap materials were exported from the United States to China, but it dropped to $2.2 billion for the first six months of this year from the first six months of 2017, the Waste30 newsletter reported.

The value of the recyclables fell to a few cents a pound. Recyclable materials backed up, with a lot of them going to U.S. landfills.

Shippers, haulers and recycling centers have been scrambling to find new markets both foreign and domestic. Some found an end-around by shipping to Taiwan, which is not subject to China’s limits, and from there the loads were shipped to China.

But recently Taiwan, Vietnam and other countries in the region imposed their own limits, which cut them off as back-doors for U.S. recyclables to get into China and enabling those other countries to avoid becoming international dumping grounds.

A year after China announced its contamination limits and six months after they went into effect, President Trump in July this year imposed tariffs on goods coming to the United States from China.

Later, more items were added to the tariff list and the amounts of the tariffs were raised.

Trump has said more Chinese goods will be added to the tariff list soon.

The backup of plastics, paper, scrap metal and other items that aren’t going to China has fostered new interest in doing more recycling in the U.S. to make new products such as railroad ties made from recyclable plastics, including plastics that always have been considered impossible to recycle.