letters
Carbon dioxide neglected
DEARSIR: I find myself fascinated with the article, “Fuels management in an environmental age,” on page 30 of the January 1971 issue of Es&T. This fascination arises because the authors of this article appear to have concluded, for unstated reasons, that carbon dioxide added to the atmosphere by combustion of fossil fuels is of no consequence. At least it is never listed in any of their tables or discussed in their text. Perhaps they would benefit by reading E. K. Peterson’s “Carbon dioxide affects global ecology” in the November 1969 issue of Es&T. Is there some reason why your own editorial staff did not pick up this omission?
W. J. Tancig Consumers Union Mount Vernon, N . Y . 10550 0 The authors of the Feature in question confined themselves to pollutants of known deleterious effect. Carbon dioxide’s effect on the environment is still a subject of considerable debate-Ed.
Food from blood
DEARSIR: Your interesting article on agricultural wastes (December 1970, page 1098) failed to mention waste slaughterhouse blood from the 130 million domestic U.S. mammals who are not Homo sapiens; they produce about 2 million pounds of blood each year as a by-product in this country. Since Americans do not normally eat products made from waste blood, such as sausages or blood puddings, and since there is only a small market for fertilizers and feed made from blood, the blood presents a serious waste problem. Our firm has developed a technique for converting the red cells of mam380 Environmental Science & Technology
malian blood into food for oysters, clams, and other filter feeding organisms. The need for aquatic animal food should grow as the agricultural industry expands. We are talking with a number of meat processors regarding use of our system for converting their waste blood into nonalgal oyster food. Cyrus Adler, president OffshorelSeaDevelopment Corp. New York. N . Y . 10038 Washday lawn watering
DEARSIR: Professor S. S . Sandhu, in a letter published in your February 1971 issue (page 9 5 ) , enumerated many advantages for discharging laundry wash water on home lawns. ES&T is a highly respected publication. Many conservation-minded citizens may take Professor Sandhu’s suggestion as an endorsed practice to alleviate detergent pollution. Since letters to the editor are published without review, perhaps a brief editor’s note should follow any letter with scientific and technological implications. For the present case, I wish to point out that the practice advocated by Professor Sandhu may cause damage to grass and other garden plants. Professor Sandhu was careful to indicate that the soil in his yard is acidic, sandy, and well-drained. This combination of soil conditions is probably responsible for his observation of favorable results following several months of irrigation with laundry water containing synthetic detergents. Under alkaline and clay soil conditions, the plants cannot long survive either the increasing salt content or the tie-up of essential metals. Normal anionic detergents contain very little nitrogen. The fertilizer value lies mainly in a supply of phosphate. These detergents are formulated of sodium salts of weak acids and thus they are rather strongly alkaline. Excessive amounts of phosphate will tie up iron, magnesium, calcium, and other essen-
tial metals needed for plant growth. The buildup of sodium salts may cause lawn damage similar to that due to rock salt used for melting ice on driveways and sidewalks. Even for well-drained sandy soil, the long-term effect of detergent on lawns is questionable. Extensive applications of agricultural chemicals in the Imperial Valley of California, for example, have resulted in excessive salt content in m w h of the land. In order to keep the area productive as an agricultural center, extensive drainage systems had to be installed. It is feared that even denser networks of drainage tiles and more frequent irrigations will be needed to reduce the soil salt content. This tends to suggest that careless disposal of chemicals on land may very well lead to undesirable effects. Before housewives take Professor Sandhu’s advice seriously, I suggest that they check out carefully the soil conditions in their yards and seek an opinion of local experts. John Yang Dept. of Civil Engineering State University of New York Buffalo, N.Y. 14214 Drinkable effluents
DEARSIR: Your Editorial in the February issue, “Effluents are tasting better and better,” (page 97) provides food for thought. The conclusion you reached is logical in light of the preceding discussion. That discussion, however, has been oversimplified. It is a practiced fact that, under some circumstances, it may become economical to recycle waste water directly. Possibly reclamation might prove to be less costly than salt water conversion. In reclaiming waste water, makeup will be required, since it will be necessary to “blow down” a percentage in order to keep mineral concentrations within tolerable limits. In a more normal situation, one
