LOL - let's burn a ton of carbon to create something that sequesters a gram!
For their next trick, they're going to cure sea level rise by preventing one drop of rain from returning to the ocean.
I'm not sure what's worse - the rank arrogance of people who think that their "making a difference" will ever be noticed, or the utter incomprehension that exists in almost everyone's minds when it comes to the concept of "big numbers". Can anyone really grok 3000gigatonnes?

A little research into reality, not propaganda, of CO2, would show that it is not a significant 'greenhouse gas' never has been, and never will be. The Earth has had an atmosphere with Twelve Times the current CO2 level in the past, [carboniferous age] was it a greenhouse? No, it was an ice age. Mars receives about half the energy from the sun as earth, but it has 2,400 times as much CO2, is it a greenhouse? No. The main greenhouse gas on earth is water vapour, Mars has non, so it is not a greenhouse, in spite of its enormous atmospheric CO2 content. The CO2 myth was started by Maggie Thatcher to justify her closing down coal pits, and to bring in Nuclear power, then someone had the bright idea of Carbon Tax. Have you ever known a politician tell lies? Have you ever known one to tell 'The truth, The whole truth, and nothing but the truth?' If you have, then I would believe in fairies and hobgoblins.

Have to agree with Christopher. OTOH, Coffee grounds are excellent for masking the smells of poo, whether human or animal. A dairy farmer in Japan get them for free from his nearby canned coffee plant and sprinkles them generously on the straw bedding for his cows, solving the odor problem that was upsetting his neighbors. It can also be used in dry composting toilets for the same purpose. such toilets can be designed to harvest the emitted methane to burn as a fuel (a dry methane digester).

Nik: You fail. Mars has a thin atmosphere, it's really small compared to to earth's atmosphere. There is a very low potential to keep that energy, it will go back to space really quickly. Earth has more way to store that energy. It's thick atmosphere, its oceans, its forests.

Hmmm? How much gas was created to heat the coffee to temperatures of 700-900 °C (1,290 - 1,650 °F)? And mgb, the Carboniferous Era was about as far from an Ice Age as one can get. Please check sources.

Just dump them under a rosebush where you get a win/win solution. The roses love them. Or toss it into your compost pile. All the rest described above is just make-work. First you have to get all of the Starbuck's on board to save them all for you, then, work, work, more work………...

Coffee grounds work as a hand cleaner like pumice. mix in some dish washing detergent and it cuts through automotive grease with no sweat. Paint, glue and tar take more effort but still come off.

'"We were sitting around drinking coffee and I looked at the coffee grounds and thought ‘I wonder if we can use this for methane storage?'" says Kemp.'
I do not buy into the anti-CO2 hysteria, but this seems like an interesting approach to capture and use methane, as opposed to just letting it vent into the atmosphere. Energy is energy, and the more efficiently we use it, the cheaper it should get...

Carboniferous was warmer than today because there was no land mass over either pole to cool things down. We are in an ice age now , the warm part, and there is a land mass at the South pole, Antarctica. We will return to cold relatively soon, say 2,000 years or so.

So if I eat the coffee grounds I sequester my own emissions and vibrate off all excess weight and quite possibly walk through walls. Cool.