C. Green Coffee Prep
Coffee is ideally 10%-14% water weight. In my work in Green Coffee in Colombia, we would strive to ship coffee as high as 16% so that it would arrive at the customer at that magic 14% moisture mark.
During the roast process you can expect to lose up to 20% of the weight of the coffee due to moisture loss and burning of oils and other interior pergamino skins in the form of evaporation, smoke and chaff.
So for every pound of finished coffee that you require, add 3.2OZ or 20% extra coffee to your drum. I found that this number works well for pulling the roast at second crack. So use this following table as a rough guide. Every coffee is different so use this as only a rule of thumb. If you roast well into 2nd crack, you will lose even more weight. So, in general, the longer or darker you roast, the more and more coffee you will have to provide to complete the volume (12OZ or 16OZ) that you intend to sell.
To restate, a vienna/french roast will take more or less 1/3 more beans to make 1 pound of coffee as compared to a full city. Plus, it will cost you more gas to get you to that point. So, in order to reduce cost per pound keep your roast times shorter and less dark if you have the choice.
Finished Roast Volume
1Lb 3.2 OZ
2Lb 6.4 OZ
3Lb 9.6 OZ
4Lb 12.8 OZ
7Lb 3.2 OZ
8Lb 6.4 OZ
9Lb 9.6 OZ
While were on the subject of green loads, the 4, 6, 8 and 12 pound drums are best rated for 4, 6, 8 and 12 pounds of green coffee, not finished coffee. That said, I have, the drums have been rated with a MAX load, that you can attempt if you have extra heat. With this method you will get decent, albeit possiblyslightly uneven roasts by adding a few degrees of temperature to my standard roast profile.
***PLEASE NOTE THAT THESE SHOULD BE CONSIDERED ROUGH RULES OF THUMB, EVERY GRILL, COFFEE, AND PERSON WILL ROAST DIFFERENTLY. USE THESE NUMBERS AS A STARTING POINT AND LEARN WHAT BEST WORKS FOR YOU AND YOUR COFFEE.***