You are correct, lots of people are working on this. Each week I encounter...
...new papers on the topic of approaches to the problem in the Engineering and Scientific Journals I read.
These papers fall into several classes, discussion of the risks associated with current practice - which is the class into which the paper cited in the OP is - papers devoted to new processes and their potential risks, and papers about potential products that might be obtained from sewage processing.
Your friend is right, heat of course, in general, ameliorates that problem, but it does not address other problems associated with the processing of sewage sludge, for example heavy metals (which was actually part of the subtext of the paper cited in the OP):
Distribution Characteristics of Heavy Metals in Different Size Fly Ash from a Sewage Sludge Circulating Fluidized Bed Incinerator
or sulfur:
Sulfur release and migration characteristic of sewage sludge combustion under the effect of organic calcium compound addition
or nitrogen:
Interaction Characteristics of Mineral Matter and Nitrogen during Sewage Sludge Pyrolysis
I selected these papers more or less at random from a search of the five major scientific journals I always at least scan and often read over the last seven years, a list that gets 100 hits (on the ACS website). A search on Google Scholar containing the term "sewage sludge" gives more than 48,000 hits since 2010.
I agree with the editorial remarks in this paper:
We Should Expect More out of Our Sewage Sludge
My environmental philosophy consists of the view that there should be no such thing as "waste," that all products of our human activities should either be useful or non-existent. My view is that if we cannot find a use for what is (currently) considered "waste," we should not generate it, or at least not generate any that cannot be combinatorially optimized to most manageable with the least amount of risk. (Scientists understand risk fairly well, even if the general public and the politicians the general public allows to rule them are completely clueless on the subject.)
Sewage sludge can be an important resource, and the resource which most concerns me, beyond the carbon sources in it is phosphorous:
Some constiuents of sewage sludge, for example, phosphorous are issues that we fail to address at our peril. Our food supply depends wholly on the phosphorous cycle. And people are thinking on a very deep level about this.
Molecular Design of Nanofiltration Membranes for the Recovery of Phosphorus from Sewage Sludge
As is the case with many major environmental problems, there is a huge divide between the upper 10% in terms of wealth, and the poorest 90%. In the case of the poorest of the poor, let's say the 3.5 billion people in the lowest half in terms of wealth, often the problem is that there is nothing for them available for the treatment of human and animal waste.
I frequently cite in this space, in another context, the Lancet paper evaluating the risks associated with various human practices and conditions, this one:
A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010 (Lancet 2012, 380, 2224–60
According to this paper, the death toll from the lack of any sanitation was responsible for close to 350,000 deaths in 2010, happily down from 700,000 deaths in 1990.
As we are seeing in China, and to some extent in India, addressing the problems of the third world generates a new set of first world consequences.
We must always think deeply about the consequences of our economy, and recognize that both in moral and intellectual spheres, there are no perfect solutions, but only optimal solutions. Perfect and optimal are very different things.
The real issue is the fight against ignorance. Unfortunately, after many years of progress against ignorance, it is now actually rising all around the world as we can see in a plethora of news sources. (Here in the United States, as we all discuss on this site, we have the most ignorant government we've had in more than a century.) But the embrace of ignorance is not merely a reflection of one's position on the political spectrum, by the way. One can see impossibly ignorant statements being made on the left that are just as pernicious as those on the right, something with which I have some personal experience. Even the Sierra Club can engage in rhetoric that is environmentally ignorant, although that is not the case with the fine link you supply.
Thank you for your comment.