Ask and you might receive
As you can see, readers aren’t shy about asking questions, and MACHINE DESIGN Editors do their best to get the answers. Global warming still seems to get some readers’ dander up, even when we don’t mention it.

Algae accounting
I am somewhat confused as to why bioreactors use an electric light source (“Algae automation,” March 5). The energy to generate oil and biomass must be provided by the light source and whatever other nutrients are supplied. So I would expect a net decrease in available energy from this process, although it could provide a way to store energy. The “pumps and motors and chillers...incur an energy penalty” as you suggest, and this is in addition to the inherent cellular inefficiency.

If the intent is simply for pilot plant development, using CCFL lights is more understandable. My own experience with fermentation systems suggests a 2,500-gallon system is rather small for commercial use. We used 1,000-gallon vessels for pharmaceutical research and they were far too small for even high-value commercial antibiotics.

Doug Pilgrim

It is absolutely true that there is an energy penalty in using the lights, pumps, and chillers — quite in addition to photosynthetic inefficiency. However, if you want to make lots of algae, you need lots of CO2 (two tons of CO2 for every ton of algae). That forces you to colocate with CO2 polluters. Large agricultural acreage doesn’t really exist next to industry, so you are forced to go with an industrial solution.

Now you can supply large tracts of solar panels to meet the artificial energy requirement, but you’re back to the same real estate (and capital expenditure) problem. A better idea is to tap waste energy in an industrial environment to supply the operating energy. Imagine a factory burning lots of natural gas — lots of CO2. And to keep things simple, select an algae that has no oil content and grows fast. Use this algae to absorb CO2, gasify it on the spot, and send it right back into the furnace. Tap waste heat through a simple cogeneration facility for the operating power. Such an industrial use may well be the first ‘killer application’ for algae. The factory operator gets fewer carbon emissions (which in and around Kyoto is worth about 100 € a ton) while generating electricity, and the energy is “free” once you build the waste-heat capture mechanism.

Algae isn’t fussy about water quality, so that could come from factory operations. And the water exiting the gasification process is now clean. The residue is fertilizer.

These benefits add up to an exciting role for industrialized algae in the years to come. Stay tuned. — Riggs Eckelberry, president and CEO of OriginOil Inc.

What’s the limit?
The item on the SQ 171 anticorrosion coating was interesting (“Anticorrosion Bearing Coating,“ Feb 5), but it would have been nice if you had included a maximum operating temperature.

Michaeil Howard

The temperature limit for the coating is 250°C. But the temperature range is limited by the bearing steel. For bearings with normal heat treatment (SN), the maximum temperature is 120°C.

Mit f reundlichen Grüßen/ Best regards—Janet Mo, NKE AUSTRIA GmbH

Cool to warming
It is very disappointing that a scientific/ technical publication like MACHINE DESIGN would take the side of the Anthropomorphic Global Warming (AGW) community. For some time now, it has grated on me every time I see an article in your magazine that gives credence to the theory that man-made CO2 is responsible for global warming. Contrary to what we read in the popular media, AGW is not “generally accepted” by most climatologists and other scientists. A substantial industry is being built on the fear mongering of AGW advocates, and it probably makes sense for you to report on technologies companies can use to cut emissions and save energy. However, references to “the greenhouse gas, CO2” makes it sound like you subscribe to the AGW phony science.

Peter Staats

Dear Mr. Staats: Which article in MACHINE DESIGN are you referring to?

Editor

I must apologize for the e-mail I sent you. In fact, MACHINE DESIGN does a good job of balanced reporting on global warming.

The article I was reading was about getting energy from algae (“Algae Automation, March 5). It mentioned “the greenhouse gas, CO2”. In fact, CO2 is a greenhouse gas but the article did not discuss man-made global warming. I clearly overreacted.

I am not saying that global warming is not occurring (although it has not been proven to my satisfaction, and if it does exist, it is not a result of man-made CO2). I am concerned that the focus on CO, cap-and-trade schemes, and other inappropriate responses will damage the economy and not help us address any global warming that may be in store. For example, there is clearly a dramatic increase in costly tropical storm damage. However the increased damage stems from increased population and building in areas subject to tropical storms. Data shows that storm frequency and intensity have not increased. If there is concern about reducing tropical storm costs, let’s create zoning laws, improve building codes, and spend money moving people out of risky areas. Lets not pretend that spending outrageous sums on reducing CO2 will solve the problem.

I could go on for pages, but you get the point.

Peter Staats

Tolerance on tolerancing
The GD&T article (“GD&T — early warning for bad designs,” March 5), had some errors. The Feature Control Frame has a compartment labeled “Datum Reference Frame.” It should be “Geometric Characteristic Symbol.” And the compartments labeled “Geometric Characteristic Symbol” should be “Datum Reference Letters”. (The corrections are in accordance with ASME Y14.5M-1994, paragraph 3.4.)

The good news is that I enjoyed the article in which the authors assert the benefits of GD&T annotation within the context of Product Development.

Kevin C. Parsons

Kevin, thanks, we spotted the error and corrected the online version. —Leland Teschler

MACHINE DESIGN for kids?
My eight-year-old daughter wants to be an “inventor engineer” when she grows up and I would love to encourage her. She has a lot of fun flipping through your magazine, but I was hoping to find the same type of content at a more age-appropriate level. Any suggestions?

William Barry

William, I don’t know of any trade magazines for eight-year olds, but you might spring for a subscription to Make magazine. It comes out four times a year and contains a lot of how-to home projects. They are mostly too advanced for eightyear olds, but maybe you can help her with a few. (Their Web site is makezine.com.) — Lee Teschler