[Vocabulary] expelling the half-digested remains in clouds of greenhouse gases, billions of tons

[ambitious-girl]

what does "expelling half-digested remains" mean? can we use "this expels or which expels" instead of "expelling"?


"Cities occupy just two percent of the land surface of the Earth but consume three quarters of the resources that are used up each year, expelling
the half-digested remains in clouds of greenhouse gases, billions of tons of solid waste, and rivers of toxic sewage.
Their inhabitants are making ruinous demands on soils and water supplies for food and on forests for timber and paper."

Source -> Inside Reading 3, unit 2: Ecopolis Now

 

[ambitious-girl]

Thanks RobertJ.

"half-digested remains" = biodegradable waste that hasn't had enough time to completely biodegrade.

Woow!! How did you know that? I was googling the net for this meaning, but I could't find anything.

What does "expel" mean here?
Is #3 definition OK?
https://www.collinsdictionary.com/dictionary/english/expel

 

[Lynxear]

I don't think all "half-digested remains" are necessarily biodegradable. I think the "half-digested remains" are the waste products of all aspects of a city. Biodegradable waste is waste that can be broken down carbon dioxide, water, methane or simple organic molecules by micro-organisms usually by natural means such as composting and digestion methods. Food and garden wastes are biodegradable as are some plastics, paper and the like. However, combustion products such as carbon monoxide, carbon dioxide, nitrogen oxides and sulfur oxides are not biodegradable. Metal waste such as that from electroplating industries is not biodegradable and often pass through the the sewage treatment system polluting water systems. Fertilizers used in the production of crops leach into water systems as well polluting them.

So "half-digested remains" is just a rather poetic way of describing city waste in general.

This sentence is a mouthful. I would break it up into two sentences

"Cities occupy just two percent of the land surface of the Earth but consume three quarters of the resources that are used up each year. The half-digested remains are expelled in clouds of greenhouse gases, billions of tons of solid waste, and rivers of toxic sewage."

 

[Rover_KE]

What does "expel" mean here?
Is #3 definition OK?
https://www.collinsdictionary.com/dictionary/english/expel

Yes.