Coffee should be had within 20 minutes of brewing, it becomes more bitter and acidic the longer it sits. And microwaving old coffee? Yuck; my mother-in-law does that.

I like the Thermos idea.  I have a nice one from when I was on crutches earlier this year and couldn't carry a cup of coffee across the room without making a huge mess.  Perhaps I will resurrect it, although to be honest, a pot of coffee tends not to go to waste at our house.

I am surprised that you didn't mention the water wasted when you brew too much coffee, then pour it down the drain because it's cold. This is why I hate those enormous coffee urns at big companies - most people only like fresh coffee, so gallons of water get wasted because people brew it fresh after it's been sitting there for a few hours.
He could also just not brew an entire pot in the morning, particularly as he seems to know exactly how much is always left over. And has he ever heard of a French press? A great way to control the exact amount of coffee /water used - and you can use the microwave to heat the water.

Organic, shade-grown, fair-trade coffee is pricey! Seems a shame to waste it. I save beans, nuke coffee at home and work--and save my resource-use eco-guilt coupons for other offenses like occasionally buying piping hot java in non-recyclable cups at corner kiosks. (I try to remember to bring my worn silver travel mug everywhere. But I forget.)

i have a coffee maker that has a thermal carafe that keeps the coffee hot for a surprisingly long time, and when it does get cold it isn't so nasty when it is reheated since it hasn't been burnt and evaporated by sitting on a hot plate.  the thermos would be the same principle, but maybe the office could invest in one of those large starbucks-type carafes? just a thought.

Any excess liquid coffee could be put on plants in the office -- with a couple of exceptions -- or poured around the roots of outside plants or in the compost pile, if you have one. Coffee grounds are good in the compost pile, too.

A neighbor of mine told me that coffee contains nitrogen. I haven't researched the matter. What I do know is that certain of my plants love that excess coffee, but don't like it more than once a week. I also put coffee liquid and grounds on some of the outside bushes and in the compost pile.

Another neighbor brings home coffee grounds for my garden from her office. Yes, it's extra work but being an enviro and not wasting stuff has never been easy.

The cautions are (1) only put it on inside plants once a week; and (2) not all plants like liquid coffee, but you usually can tell after a couple of weeks which plants don't like it.

I can't believe no one suggested a pot with a thermal carafe.  I won't mention brand names, but I have a 12-cup pot with a thermal carafe that will keep coffee hot enough to drink for about 12 hours (and I, too, demand my hot drinks HOT.  Then I refrigerate the left-overs and make iced coffee for a quick-pick-me-up.

No waste, no reheating good coffee (yuck), and no appreciable additional energy use.

I don't want to insult PCD or Umbra, but this question and its answer (save the thermos) are flawed.

If you drink coffee (and by coffee I mean coffee, not coffee flavored sweetened milk) because you enjoy the taste, then you cannot possibly reheat it -- it is easily burned and quickly tastes like something that needs milk and sugar. The question of reheating coffee is akin to "what's greener, buying conventionally grown food or dumpster diving for your meals?" Clearly, dumpster diving for food is about as low impact as you can eat ... but yuck.

The best solution of all to on-demand hot coffee could be a little known technique, I'll call it "cold pressed" for lack of more knowledge, that is more labor intensive but lasts much longer  (I have only seen it served in a Fairbanks, AK health food store). "Cold pressed" coffee involves grinding beans, wrapping the grounds in layers of cheese cloth or some other (preferably organic cotton) cloth, soaking the ball in cold water, then hanging it and collecting the concentrated coffee that drips out of it.  Put the product in a bottle and add a measured amount (to taste) to a cup of hot (microwave heated if you like) water -- and enjoy the smoothest cup of coffee goodness that you've ever had. No heat is applied to extract the coffee from the beans so there is much less acid and the nasties that are extracted by hot water brewing. Put the bottle of concentrate in the fridge and it will keep for days (or so I'm told). If only I wasn't so lazy.

So, PCD, when you need another cup of hot coffee and the pot is cold (you might blame me, I often turn off the burner before it gets totally gross), just let me know and I'll take care of the dirty work, you don't have to know what eco-sins were committed in its making.

(BTW, the 3 lb. bag of organic coffee from Costco isn't half bad and costs less than 1 lb. of most good non-organic brands.)

Okay... we're discussing one of my favorite subjects ~ coffee! As one who has been a coffee snob for the past 30 years (read; one who has purchased coffee beans at specialty stores and never the canned, store variety), I can attest, there is NOTHING as delicious as a good cup of coffee to put one in the right frame of mind. As mentioned, coffee should not be allowed to go cold and should be used shortly after brewing. With regard to discarding coffee or spent coffee beans (from a French Press or used coffee filters), I have always spread the used coffee either in a garden or on a lawn. It is true that coffee beans contain a lot of nitrogen which is good for the overall health of most outdoor plants (within reason, of course). But coffee should NEVER be reheated, that breaks the coffee down and takes all the flavor away. I guess the only thing I would add is make sure the coffee is stored in cool, air-tight, dark area. Don't boil the coffee and buy the best coffee you can afford. Two of life's great pleasures, good coffee and good micro-brewed (or home brewed) beer... but that's another subject left to another time.

PCD sounds like a bright (and handsome) lad who likes his job and is respected by his colleagues and whoever he works for should treat him to various rounds of drinks at the next holiday party  :)

I'm amazed at Umbra's answer and all the responses to this query, I didn't know how much was involved in wondering about something that really just takes up .0001% of my daily decision process, but with all the pots my co-workers and I go through, I'm sure the energy it takes to meet our consumption is equally amazing.

I personally like the giant thermos idea, especially if I can just take a kings ransom of coffee and horde it for my own caffeine infused greediness, not to mention that although nuking the remaining java would make me feel better about things, I'm in the school of not zapping the delicious organic beans that Tom selflessly brings to the office regularly. Anyway, it's a great holiday gift idea for whoever has stake in my happiness (friends, girlfriend, mom, that's a hint!)

Somebody mentioned this upstairs, but I'll go further and offer that a very inexpensive (about $25 online) little coffee-maker, the AeroPress, is FANTASTIC and solves both taste and energy/water issues.

AeroPress is small enough to bring along on trips, and is a good workplace companion. I use nothing else, and, for any cynics in the studio audience, I do NOT work for the Aero-people.

Similar in concept to a french-press, but much more precise, it's made of (good) plastic, designed by the same Stanford prof. that made the Aerobi frisbee. Comes with filters and a scoop, and makes the best coffee I've ever had at home by far. There's no plastic taste, even when new and far outperforms any french-press I've ever used.

Nuked coffee makes me gag. Just say no. Reheated coffee isn't fit for human consumption.

Instead, microwave a cup of water... no need to boil it for the AeroPress, grind your coffee (burr grinder if possible) then mix in the central chamber. Push the infusion through the filter directly into your cup, compost the grounds, rinse off (no need to wash) the little device and drink yer brew. So smooth.

Don't believe me... I was convinced by consistently positive reviews on several coffee-fanatic websites (just Google "AeroPress review") comparing it to fancy Italian coffee machines. It's true. Fantastic.

Great coffee, no wasted water or electricity. It's a very pleasant little "coffee ceremony" with a very satisfying result.

The previous posts have some excellent ideas about reducing energy use and wastefulness in our coffee drinking habits.  It seems to me that the biggest waste may come from making more coffee than is needed, even if the excess is used to water plants or as a soil additive.  For example, if I fill my 10 cup coffee maker with the organic coffee grind that I bought, and end up only drinking half of the brew, I'm in essence wasting half of the beans.  While perhaps trivial if this overbrewing rarely happens, but I suspect that cumulatively there's a lot of coffee poured out and a lot of beans that didn't have to be used if the actual need was calibrated more precisely. (Excellent argument for one cup at a time brewing.)  Those wasted coffee beans were obviously grown somewhere, taking up land, using various agricultural inputs, roasted with various energy consuming techniques, transported, ground, sold, and carried to the ultimate user.  If I am correct, the energy differential between reheating versus brewing a new pot is minor compared to the waste of resources, including energy, of using more beans than absolutely necessary and then pouring out the excess coffee produced.  Make only what you need and if there's excess, consider putting it in a storage container, refrigerating it overnight, and reheating it the next day (I suspect there are some coffee purists who are gagging at the thought <smile>.)  A few experiences with cold coffee reheated the next day (unless you happen to like cold coffee) and I predict you'll be more cautious with how much you brew.  

"Be the change" hit the nail on the head. The amount of resources for one cup of coffee is astounding. If it is sun grown coffee, there are even greater ramifications-pesticides, herbicides and lost tropical forest habitat for songbirds and other creatures. Best to only make what you use (or as Tom suggests, stop drinking it altogether.) If that is not possible,do whatever it takes to drink the rest. It won't taste as good as fresh hot coffee but it will make you appreciate that next fresh cup more, make you less wasteful, and less inclined to brew too much in the first place.

In my opinion, the most environmentally friendly way to make coffee is also that which will keep it hot and good-tasting the longest.
Do not use any kind of coffee machine. Use a paper filter in a filter holder.  Put the filter holder directly on top of the opening to a good-quality thermos bottle.
Heat water in the microwave and pour it into the filter. This takes only slightly more time that using a coffee maker, but it is well worth it in terms of the resulting taste, not to mention energy savings.
Note that the filter holder, the vessel used to heat the water, and the thermos bottle do not need to be cleaned with soap and water, thus saving enormous amounts of water. Once in a while they could be rinsed out. A thermos bottle used for coffee should never be used for any other liquid because it will leave the coffee taste in it, and it should be rinsed with water and never scrubbed with soap.
The coffee grounds can be put in the garden.
With the exception of heating water in a microwave and putting the grounds in the garden, this is what nearly the entire country of Brazil does.  Every home has at least one thermos, and fortunately we also have Arabica beans down here.
The AeroPress coffee maker looks like it will make great coffee, but will need copious quantities of water used to clean it between each cup.

...and one other evil of dumping the remaining coffee in the pot is caffeine in our ground water.  I have to agree that re-heated coffee is pretty vile, but then, I have tossed back double-strength Folgers with a Vivarin whilst on a deadline, so....

I have a Krups 4-cup coffe brewer.  Everyone laughs at it, but I've had it since I was 19 and started drinking coffee and that was a good long time ago. It is still trucking along and I still like not having to brew a big pot of coffee for little ole me.

I like to consider myself a coffee connoisseur sometimes, just for kicks.  Anyway, reheating coffee is usually gross.  By the time the coffee gets cold it becomes bitter and if you reheat it, it still has the bitter rank taste.  Here are my two suggestions.  First, as other suggested try a well insulted thermos.  I usually bring a travel mug with me, and I've even found one at Starbucks which holds the heat very well.  Secondly, there are some really nice single serve coffee makers out there.  At home, I have my regular coffee pot maker and a single serve.  The single serve is great, b/c you can make just one cup at a time, and they are usually small enough to keep at a desk.  If you go this route, I recommend purchasing one that has a resuable filter, and doesn't use "pods."  If you buy one that uses coffee pods, then you are limited to the brands of coffee you can use.  I hope these ideas help!

Sarah

Umbra, you disappoint me. You skimmed the surface of this question. Blah.