INL Science Feature: INL scientists help harness bacteria power to brew eco-friendly plastic from waste

Three samples of premium wood-plastic composite lumber sit in a stack on a shelf in David Thompson's office at Idaho National Laboratory. The dense, fine-grained boards are uniformly colored in shades that range from light to dark brown.

All three boards match each other in strength and durability. But one of the boards has two special ingredients: plastic made by bacteria, and the same harmless bacteria that made the plastic — by eating wastewater.

Eat more food than you can use, and your body will stockpile the surplus in all sorts of curvaceous and unsightly ways. Many species of bacteria do something similar.

"Plastic, to these bacteria, is like fat," says Thompson, an INL biochemical engineer. Given an abundance of sugars, alcohols or other simple carbon sources, the bacteria will ferment the molecules for energy and string together the leftovers into long chains, or polymers, that they can stash for use in leaner times. Many of these polymers are actually types of plastic called polyhydroxyalkanoates, or PHA for short.

What bacteria make, they can also break down. All three of the sample composite boards in Thompson's office are too dense to absorb much water, which helps them resist rotting and cracking better than natural wood. But if you chipped up Thompson's bacteria-PHA composite board and buried it in an active compost pile, it would biodegrade completely in three to six months. In contrast, the petroleum-based plastics in standard wood-plastic composites could sit in your backyard or in a landfill for hundreds of years or more before breaking down completely.

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For fun: Asians and blacks - the extremes in interracial marriage

This is a follow-up on a NYTimes story, Black Women See Fewer Black Men at the Altar. The range and extremes in this cursory analysis of interracial marriage rates are pretty striking:

Of all 3.8 million adults who married in 2008, 31 percent of Asians, 26 percent of Hispanic people, 16 percent of blacks and 9 percent of whites married a person whose race or ethnicity was different from their own. Those were all record highs.

Well, since Asians are the smallest ethnic group of the four, just by sheer odds we should be marrying outside our race ('marrying out') more often than the other groups. But how many of the interracial marriages are due to preference and how many of them are what we would expect just by the numbers?

If your choice of whom to marry were completely independent of race, the chance that you'll marry someone from another race would be about like the chance you'll run into someone from that race on the street. If we take the U.S. Census Bureau data from 2004 (most contemporary survey with all four of the largest races), the single (not married or separated) population over age 15 is:

3.6% Asian
13.3% Hispanic
16.5% black, and
66.5% white.

So since 96 of every 100 single people (13.3+16.5+66.5 = about 96) in the States are not Asian, you'd expect about 96 of every 100 Asians to marry out.

But only 31 of each 100 did, so it looks like Asians show some tendency to marry each other ('marry in') more than they marry out. Let's look at some ratios to see how the same-race preferences compare across the races:

	intermarriage rates
race	expected	/	actual	=	ratio
Asian	96.4	/	31	=	3.1
Hispanic	86.7	/	26	=	3.33
black	83.5	/	16	=	5.22
white	34.5	/	9	=	3.83

The higher the ratio, the more likely that race is to 'marry in'. Asians are, again, the biggest miscegenators, but not by a lot. Blacks, on the other hand, are far more likely than the other racial groups to marry each other based on what we would expect from race-independent marriage. We can speculate on the contributing factors - prejudice, prison, education, age structure, other socioeconomics - but I don't have any data to support or refute any of them for now.

By the way, in 2004, the percentage of each racial group married without separation:

Asians 61%
Hispanics 50%
blacks 34%
whites 57%.

Asians are almost twice as likely to be married as blacks.

[In a New York Jewish accent] Talk amongst yourselves.

WHERE I GOT MY NUMBERS:

In addition to the referenced NYT story, I pulled March 2004 Census Bureau Community Survey data from these sources:

http://www.census.gov/population/socdemo/race/api/ppl-184/tab2.html
http://www.census.gov/population/socdemo/hispanic/ASEC2004/2004CPS_tab2.1.html
http://www.census.gov/population/socdemo/race/black/ppl-186/tab2.html

From those tables I added the numbers of widowed, divorced, and never married to get the following numbers:

3,623,000 single asians >15 both sexes in March 2004
13,294,000 single hispanics >15 both sexes in March 2004
16,499,000 single blacks >15 both sexes in March 2004
66,408,000 single whites > 15 both sexes in March 2004
99,824,000 single people total in March 2004

The percentages of each racial group that are married are taken directly from the linked tables. Yes, I am leaving out Inuit/American Indian, Hawaiians and other Pacific Islanders, as well as mixed-race. They account for, respectively, 0.8%, 0.14%, and 2.3% of the population, too small a percentage for the CB to have useful data on them.