Thursday, October 8, 2015

Up in smoke

Gene Towne and I were working on revising a paper reviewing what is known about the effects of differences in the timing of burning on grasslands and grazers.

We had written "burning in late-April after the green vegetation has emerged, exacerbates smoke production and accompanying air pollution, which is at the forefront of the burning controversy."

This sentence seemed obvious to us. If you burn green biomass, it's smoky as heck.  Still, the sentence did not have a citation. Rightly so, it should have.

I spent some time going through papers to see if what we had observed empirically had basis in the literature.

After a few hours reading papers, it seems that the statement wasn't wrong, but I did make a mistake in not reading these papers sooner. Probably the best paper was Andrae and Merlet from 2001, which is frustrating because I apparently could have learned all of this 15 years ago.

1) Smoke is complex. It contains O3, CO, water vapor, NOx, HCN (!), SO2, CH4, C2H2, xylene, benzene, etc. as well as particulates of certain sizes.

**Technical point: smoke researchers talk a lot about emission ratios (amount of a product produced in a fire relative to a standard like CO2) and emission factors (same, but relative to amount of biomass burned). They also talk about CE, combustion efficiency, with is an emission ratio of all the products besides CO2 relative to CO2 produced in a fire.

2) Fire is complex. It has stages: ignition, flaming + glowing + pyrolysis, glowing + pyrolysis (a.k.a. smoldering), glowing, and extinction. Each has different chemistry and emissions.

3) Flaming involves relatively complete oxygenation (burning) of products. Smoldering does not. Smoldering (burning without flame) is more likely to produce some products like CO and NH3 than flaming, which is more likely to produce products like CO2 and NOx.

4) It's interesting to read how stuff catches fire. When biomass starts to burn, the first step is the drying/distillation step. This releases water and volatiles. Then comes pyrolysis with "thermal cracking" of the molecules which produces char, tar, and volatiles. Here, stuff is breaking up, but not burning. As the biomass gets hotter, the tar and gas begin to oxidize, which produces the flame.
occurs. Once the volatiles have burned off, then the biomass begins to smolder (glowing fire) and many of the incomplete oxidation products are produced.

For us, we're likely to rewrite the sentence a bit to acknowledge the complexity of fire and smoke.

In all, when green grass is burned, it's nitrogen concentration is higher than senesced grass, which leads to greater production of NOx, which is a precursor to ozone production that causes health problems. Whether green grass has a lower combustion efficiency hasn't quite been resolved (Mebust and Cohen 2013). It should be lower with wetter biomass, but this apparently hasn't been definitively demonstrated. If so, then burning green vegetation is going to produce a lot more junk.

Monday, October 5, 2015

Investing for research

Just a mini thought here.

In economics, there are a number of theories on how entities invest. One of those is has to do with the relationship between the amount of investment and interest rates.

Essentially, theorems such as the marginal rate of efficiency or the marginal rate of investment state that firms continue to invest until the marginal rate of return is no different than the interest rate. In short, when making a decision on where to invest money, money will always be invested in the investment that produces the highest rate of return, until there are no options that differ than the prevailing interest rate.

By analogy, when governments are deciding how allocate scare research dollars, similar economic decisions should be at play.

In reality, these decisions are nothing close to rational, in the economic sense.

For one, we cannot quantify the rate of return on investing research dollars. Comparing two proposals for funding, reviewers likely can estimate the rate of return. The equation is something like: # of publications x impact factor of likely journals**.

**This formula is likely discounted a bit for age. Old researchers are more likely to publish, but have a shorter lifetime return on investment. Funding young researchers before tenure makes it more likely they will be publishing in 10 years...

At a broader scale, this type of analysis is impossible or irrelevant. Funding agencies need to decide whether to invest in one discipline vs. another. This equation is useless for deciding whether to invest in physics vs. biology, for example.**

**If it was used, it would just favor the more prolific discipline. Publishing papers is not the likely goal for funding agencies, per se. Papers aren't bitcoins. 

The number of likely citations is also not a good metric, because it's circular. The number of times papers in a discipline are cited on average are determined by the number of papers published in that discipline (and the average number of citations in a typical paper).

If we cannot use expected rates of returns on publications, then how do we assess worth?

This is the Achilles' heel of rational investing in science. We cannot find a common currency to evaluate the relative worth of research.

Without this, funding becomes irrational.

Right now, changes in funding levels occur at the margins. Politicians and directors do not regenerate funding levels each fiscal cycle. Instead, they make a case that funding for one area should be increased or decreased relative to what it is currently. There are no equations that are employed to determine relative funding levels or relative changes in funding levels.

Until we have a concrete way to assess the value of research, either in terms of dollars, or social equity, or longevity, funding is likely to be irrational.

Stepping back, not only the relative amounts of funding, but absolute amounts of funding for research need development. In the US, NIH budgets are 4x higher than NSF. Why the relative difference is one question. Another, is why are there combined budgets almost $40 billion? Should they be $20B or $80B?

If the decisions are fundamentally irrational (economically), then we either need to make them economically rational, or commit to irrational (economically) arguments.