Obtaining Practical and Accurate EIL Measurements – Part II
June 18, 2009
Part I of this post discussed the energy inputs for compiling, writing and designing a book. Part II will concern the physical production hard copies of that book.
First we need to examine Direct energy inputs.
The book is printed on a good quality laser printer and comb-bound. The laser printer consumes energy from the local utility company power grid. The binding equipment only uses human labor. It punches the pages (with about 30 holes), collates the pages and covers, and stretches out and places the plastic comb.
The laser printer system comprises a combination CPU/monitor (an iMac) and a laser printer. The iMac is rated at maximum current of 6.75 Amps run at 120 V. Per the Standards, we use this maximum current rating. Arguably that is too high, but there are so many energy inputs that we are neglecting, that this is a reasonable approach. Further, the iMac and laser printer are substantial active while printing, so we are not greatly over-counting energy inputs. The laser printer runs at a maximum current of 5.5 Amps run at 120 V. This system must run for 15 minutes to product each book. So the iMac contributes 0.12 kilowatt hours (kWh or kwh) and the laser printer contributes 0.10 kwh for a total of 0.22 kwh.
Human labor is not trivial. Each booklet requires an average of 18 minutes, mostly spend during binding. Great care must be taken during the binding process, or the books become damaged. Using the baseline figure of 0.1 kwh energy input rate per person, per the Standards, 18 minutes of labor results in 0.03 kwh of energy inputs.
Therefore, direct Energy Added Inputs are 0.22 kwh + 0.03 kwh for a total of 0.25 kwh per book.
Next, we consider Indirect energy inputs.
These books are produced in an office setting, so indirect energy inputs for lighting HVAC (heating, ventilation, and air conditioning) need to be added. A fairly easy way to determine overhead energy is to take the total of energy used by the office, and subtract any energy that can be directly allocated to the production of products. Anything left over is indirect energy. For this reason, it is often easier to calculate direct energy inputs first. If a company produced more than one type of product, then indirect energy will need to be allocated to units of product on a rational basis, such as time required to produce each unit of product.
This small office consumes 100 kwh per month in overhead energy, and is staffed 160 hours per month, and spends 50% of its time producing books. Therefore, 50 kwh of indirect, overhead energy must be allocated to the books. If 3 books are produced per hour ( x 160 hours x 50%), the the overhead must be divided by 240 units of product (240 books). Since the office spends 50% of its time producingbooks, then this proportion of overhead will be assigned to book production. So then, 100 kwh per month x 50% divided by 240 books equals 0.21 kwh of indirect energy inputs per book.
So then, the Direct and Indirect energy inputs per book are combined to report the total Energy Added Inputs we have per book, which here is 0.25 kwh + 0.21 kwh equals 0.46 kwh per book to produce the book. From Part I, we have 0.19 kwh required per copy of the book to compile, write and design the book. Adding 0.46 kwh + 0.19 kwh equals 0.65 kwh. So the book would be labeled “Energy Inputs Added: 0.65 kwh”. The sources (and their percentages of contribution) could bereported as well.