Burning natural gas inside a peat-smoker carries risks.
When I introduced into the text the issue of Nitrosodimethylamine Bill Lark saw it as problematic—even though he had brought the topic to my attention. I altered the text but Bill declared it still wrong. No matter how I re-cast it, he could not be satisfied. Exasperated, I consented to him writing the entry. He wrote the version below and it was published:
post-malt peating Bill Lark invented a way to imbue barley with peat smoke after it is malted. It is a gentle process that produces a subtle “bushy” note in the spirit. Because it uses previously malted barley it does not require the addition of sulphur in the smoker.
No mention of the N word. N-nitrosodimethylamine. No one, not even Chris Middleton, wanted that word mentioned. The 'problem' with nitrosamine is that its presence, at a high enough level, invokes the "C- word": Cancer. High nitrosamine levels show a strong correlation with liver and oesophageal cancers; but on the other hand, because the levels would not be high nitrosamines is just a bogeyman—so why raise it? Answer: because it is better in than out, and also because Lark's corrected text introduced its own error.
On the face of it, post-malt peating is doing the very opposite of what Bill claimed for it: the "sulphur-free process" is not removing but creating N-nitrosodimethylamine.
As the photo accompanying the segment (page 38) showed, the peat is direct-fired by a natural gas burner alight under the peat and trays of barley with no sulphur in sight. But on Cocktailchemistry Jordan explained that "the temperatures produced by gas flames ... increase the formation of nitrogen oxides from the nitrogen present in air. Those nitrogen oxides ... react with nitrogen-containing compounds in the malt to produce nitrosamines." That is, it is the natural gas that is creating the nitrosines. The solution is simple. According to the encyclopaedic work Whisky: Technology, Production and Marketing: "to reduce nitrosation during kilning, sulphur dioxide or indirect-fire kilns are used in the malting". The authoratative WhiskyScience website confirms that "The formation of nitrosamines can be blocked by... burning sulphurous fuel such as sulphur-containing coal, rock sulphur or gaseous suphur dioxide." And Jordan went on to specify the nitrosine-free technique to be used during peating, which must be direct-fired: "[because] peat fires .. produce nitrogen oxides, it is important to avoid flaring while burning peat, as that will increase the production of nitrogen oxides. To prevent this, sulfur is burned alongside the peat, which forms sulfur dioxide, which reduces the pH of the malt and inhibits the formation of nitrosamines. This process also occurs naturally in kilns heated by coal and oil burners, as these fuels contain fairly high levels of sulfur. In comparison, natural gas contains very low levels of sulfur, which likely contributed to the formation of nitrogen oxides when it was used to dry malt."
In short, do NOT direct-fire or use natural gas, but if you do both: DO burn sulphur. Do look at the photo again closely. There is no assuaging sulphur being burnt. Sulphur is not the cause, it is the cure. By not using sulphur, Lark may (I cannot know without seeing analytical test results) be adding N-nitrosodimethylamine to its whisky.
WAIVER It is also crucial to recognise that even in the worst case scenario, the levels created will not constitute a significant health risk. Tobacco, for example, contains 1000 times the n- levels of whisky. I raise the topic because it is illustrative of the hyper-sensitivity of the industry to criticism as well as its ignorance.